cubecl_runtime/

client.rs

use crate::{
    config::{TypeNameFormatLevel, type_name_format},
    device::HardwareIdentity,
    id::{GraphId, KernelId},
    kernel::CubeKernel,
    logging::ProfileLevel,
    memory_management::{MemoryAllocationMode, MemoryReport, MemoryScope},
    server::{
        BufferBinding, Collective, CommunicationId, ComputeWait, CopyDescriptor, CubeCount, Handle,
        KernelArguments, KernelResource, MemoryLayout, MemoryLayoutDescriptor,
        MemoryLayoutStrategy, PeerBinding, PeerMemory, ProfileError, ProfilingToken,
        ReduceOperation, Reduction, Server, ServerError, ServerStorage, ServerUtilities,
    },
    storage::{ComputeStorage, ManagedResource},
    throughput::{
        ThroughputBenchmarker, ThroughputCache, ThroughputError, ThroughputKey, ThroughputValue,
    },
};
use alloc::{boxed::Box, format, string::String, sync::Arc, vec, vec::Vec};
use core::any::{Any, TypeId};

mod group;
#[cfg(not(target_family = "wasm"))]
mod lazy;

use cubecl_common::{
    bytes::{AllocationProperty, Bytes},
    device::{DeviceId, ServiceId},
    device_handle::{CallError, CallResultExt, DeviceHandle},
    profile::ProfileDuration,
};
use cubecl_environment::{backtrace::BackTrace, future::DynFut, stream::StreamId, sync::Mutex};
use cubecl_ir::{DeviceProperties, ElemType, TargetProperties, VectorSize, features::Features};
use cubecl_zspace::Shape;
pub use group::*;

#[allow(unused)]
use cubecl_common::profile::TimingMethod;

/// Work that waits on the host for its peers, a communicator's setup and a transfer's two
/// halves, queues on every device in the order this hands out.
static PEER_ORDER: Mutex<()> = Mutex::new(());

fn repeated_device(device_ids: &[DeviceId]) -> Option<DeviceId> {
    device_ids
        .iter()
        .enumerate()
        .find_map(|(i, id)| device_ids[..i].contains(id).then_some(*id))
}

/// Flushes the device's queue when dropped.
struct FlushOnDrop<'a>(&'a DeviceHandle<dyn Server>);

impl Drop for FlushOnDrop<'_> {
    fn drop(&mut self) {
        self.0.flush_queue();
    }
}

/// The `Client` is the entry point to require tasks from the `Server`.
/// It should be obtained for a specific device via the Compute struct.
pub struct Client {
    device: DeviceHandle<dyn Server>,
    utilities: Arc<ServerUtilities>,
    stream_id: Option<StreamId>,
    /// Loads the client of another device of the same runtime.
    load_peer: fn(DeviceId) -> Client,
}

/// A captured graph produced by [`Client::stop_capture`]: a recorded
/// launch sequence that [`replay`](Graph::replay) re-runs against its original
/// buffers, skipping the launch path it was recorded from. Cheap to clone
/// (shares one backend graph).
///
/// The graph itself lives in the backend server, referenced here only by
/// [`GraphId`]; this handle holds a reference-counted owner that releases the
/// backend graph once the last clone drops. The graph replays against the exact
/// device buffers used during capture. The caller keeps those input/output
/// [`Handle`]s alive and, each iteration, writes fresh inputs into the input
/// handles (same device pointers) and reads the output handles after replaying —
/// see [`Client::stop_capture`].
///
/// **Stream ordering.** [`replay`](Graph::replay) always dispatches on the
/// stream the graph was captured on, but input writes and output reads go on the
/// *writing client's* current stream. They are ordered against the replay only
/// when they land on that same stream, so keep the client pinned to the capture
/// stream (via [`set_stream`](Client::set_stream)) — or issue all writes,
/// replays, and reads from the same unpinned client — for the whole decode loop.
/// Refreshing inputs from a client on a different stream races the replay and
/// silently feeds it stale data.
pub struct Graph {
    inner: Arc<GraphHandle>,
}

impl core::fmt::Debug for Graph {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("Graph")
            .field("id", &self.inner.id)
            .field("stream_id", &self.inner.stream_id)
            .finish()
    }
}

/// Reference-counted owner of a backend graph. Its [`Drop`] ships the release to
/// the server actor, so the last [`Graph`] clone frees the backend graph on the
/// thread that owns it.
struct GraphHandle {
    id: GraphId,
    device: DeviceHandle<dyn Server>,
    stream_id: StreamId,
}

impl Graph {
    /// Replay the captured launch sequence — every recorded kernel re-run
    /// against the buffers it was captured with, on the stream it was captured
    /// on. Self-contained (the handle owns its device handle); no client
    /// needed.
    ///
    /// How much of the launch path this skips depends on the backend: a
    /// hardware graph (CUDA, HIP) replays as one dispatch, while a software
    /// graph (wgpu) re-encodes the recorded dispatches from prebuilt state.
    /// Either way pipeline lookup, binding resolution and metadata upload
    /// happened once, at capture.
    ///
    /// Blocking only on the enqueue: [`replay`](Self::replay) waits for the
    /// device thread to accept the dispatch and hands back what that enqueue
    /// said — an unknown or destroyed graph, a refusal — then returns without
    /// waiting for the device. A failure also leaves the graph's write set
    /// carrying it, so a read of those buffers keeps failing until a replay
    /// lands.
    ///
    /// The wait costs end-to-end throughput nothing: the device-thread work
    /// happens either way, and blocking here only stops deferring it to the
    /// next sync. What it does move is the caller-visible latency of this
    /// call, from the cost of posting to a channel to the real cost of
    /// enqueuing the pass — so a benchmark reading this column is reading
    /// latency, not throughput.
    ///
    /// # Safety
    ///
    /// The dispatch re-runs the recorded kernels against the raw device pointers
    /// captured with them; nothing validates those buffers still exist or are
    /// unshared. The caller must guarantee, until the replay's work completes on
    /// the stream:
    ///
    /// - **Liveness** — every [`Handle`] the captured kernels read or wrote is
    ///   still allocated. Freeing one returns its memory to the pool, and a
    ///   later replay reads or corrupts whatever the allocator has since placed
    ///   there.
    /// - **No concurrent use** — no other stream or thread touches buffers the
    ///   graph reads or writes while the replay executes; the replay is ordered
    ///   only against work on its capture stream.
    /// - **Same-stream refreshes** — input writes and output reads are issued on
    ///   the capture stream (keep the client pinned to it via
    ///   [`set_stream`](Client::set_stream), or do everything from the
    ///   one client), so they order against the replay instead of racing it.
    pub unsafe fn replay(&self) -> Result<(), ServerError> {
        let id = self.inner.id;
        let stream_id = self.inner.stream_id;
        self.inner
            .device
            .submit_blocking(move |server| server.replay(id, stream_id))
            .closed_as_error()
    }
}

impl Clone for Graph {
    fn clone(&self) -> Self {
        Self {
            inner: self.inner.clone(),
        }
    }
}

impl Drop for GraphHandle {
    fn drop(&mut self) {
        let id = self.id;
        let stream_id = self.stream_id;
        // Destroying the raw executable must happen on the server actor (the
        // only thread allowed to touch it) and only once in-flight replays have
        // completed — `replay` returns at enqueue time, not completion. Ship the
        // release to the actor; the backend syncs the stream before it destroys.
        self.device
            .submit(move |server| server.graph_destroy(id, stream_id));
    }
}

/// A profiling window opened by [`Client::profile_start`], closed by
/// [`Client::profile_end`] or dropped by [`Client::profile_abandon`].
///
/// It remembers the stream it was opened on, so closing it from another
/// thread still closes it on that stream. It is a plain value with no
/// [`Drop`]: a window that is neither ended nor abandoned stays open on the
/// server.
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub struct ProfileWindow {
    /// The stream the window was opened on.
    pub stream_id: StreamId,
    /// The server's token for the window.
    pub token: ProfilingToken,
}

/// Where a [`Client::profile`] window opens on its stream.
#[derive(Debug, Clone, Copy)]
enum WindowOpens {
    /// Where the stream is: everything the closure enqueues is in the window.
    Now,
    /// At the next kernel launched, for a window around one launch: the host
    /// preparing that launch stays out of it. See [`Server::start_profile_at_launch`].
    AtLaunch,
}

/// The state a `DeviceHandle` reaches, seen as the server it is. A client
/// keeps this cast, not the server type, so every operation reads the same
/// whatever backend is underneath.
fn as_server<S: Server>(state: &mut dyn Any) -> &mut dyn Server {
    state
        .downcast_mut::<S>()
        .expect("State type mismatch in the device registry")
}

impl Clone for Client {
    fn clone(&self) -> Self {
        Self {
            device: self.device.clone(),
            utilities: self.utilities.clone(),
            stream_id: self.stream_id,
            load_peer: self.load_peer,
        }
    }
}

impl Client {
    /// The runtime name on this device, as logs and cache keys show it.
    pub fn name(&self) -> &'static str {
        self.utilities.name
    }

    /// Create a new client with a new server.
    pub fn init<S: ServerStorage>(device_id: DeviceId, server: S) -> Self {
        Self::try_init(device_id, server)
            .expect("Can't create a new client on an already registered server")
    }

    /// Register a server, returning an error if its device is already registered.
    pub fn try_init<S: ServerStorage>(
        device_id: DeviceId,
        server: S,
    ) -> Result<Self, cubecl_common::device_handle::ServiceCreationError> {
        let utilities = Server::utilities(&server);
        let context = DeviceHandle::<S>::insert(device_id, server)?.seen_as(as_server::<S>);

        Ok(Self {
            device: context,
            utilities,
            stream_id: None,
            load_peer: Self::load::<S>,
        })
    }

    /// Load the client for the given device, starting a server of type `S`
    /// there if none runs yet.
    pub fn load<S: ServerStorage>(device_id: DeviceId) -> Self {
        let context = DeviceHandle::<S>::new(device_id).seen_as(as_server::<S>);

        // This is safe because we now know the return type of [`DeviceHandle::utilities()`].
        let utilities = context
            .utilities()
            .downcast::<ServerUtilities>()
            .expect("Can downcast to `ServerUtilities`");

        Self {
            device: context,
            utilities,
            stream_id: None,
            load_peer: Self::load::<S>,
        }
    }

    fn stream_id(&self) -> StreamId {
        match self.stream_id {
            Some(val) => val,
            None => StreamId::current(),
        }
    }

    /// The stream its launches go out on, on its device's service: what a
    /// [`StreamModeOverride`](crate::execution::StreamModeOverride) sets the
    /// mode of.
    pub(crate) fn service_stream(&self) -> crate::execution::ServiceStream {
        crate::execution::ServiceStream {
            service: self.service_id(),
            stream: self.stream_id(),
        }
    }

    /// The service this client reaches: what its handles are stamped with.
    pub fn service_id(&self) -> ServiceId {
        self.device.service_id()
    }

    /// Whether the server behind this client is an `S`. The client is erased
    /// over its server type, so a caller naming one has to be checked here,
    /// before a downcast on the device thread turns the mismatch into a panic.
    fn is_service<S: 'static>(&self) -> bool {
        TypeId::of::<S>() == self.service_id().service
    }

    /// A `Peer` argument as bound here: an ordinary buffer on its own device,
    /// a peer binding on another.
    ///
    /// # Panics
    ///
    /// On memory of another runtime, or of a device this one cannot address.
    #[track_caller]
    fn bind_peer(&self, peer: PeerBinding) -> KernelResource {
        let own = self.service_id();
        let service = peer.binding().service;
        if service == own {
            return KernelResource::Buffer(peer.into_binding());
        }
        assert!(
            service.service == own.service,
            "a peer buffer of {service} was launched on {own}, of another runtime"
        );
        assert!(
            self.reaches_peer(service.device),
            "{own} cannot address the memory of {:?}: check `can_access_peer` before \
             launching with a buffer of another device",
            service.device
        );
        KernelResource::Peer(peer)
    }

    /// Whether kernels here can address the memory of `device`, cached per pair.
    fn reaches_peer(&self, device: DeviceId) -> bool {
        if let Some(reaches) = self.utilities.peer_access.read().get(&device) {
            return *reaches;
        }
        let reaches = self
            .device
            .submit_blocking(move |server| server.can_access_peer(device))
            .unwrap_or(false);
        self.utilities.peer_access.write().insert(device, reaches);
        reaches
    }

    /// Whether `binding` addresses this client's device. Memory coordinates
    /// mean nothing on another device, so a foreign binding is refused here,
    /// before anything is submitted, rather than read there.
    fn local(&self, binding: &BufferBinding) -> Result<(), ServerError> {
        let client = self.service_id();
        if binding.service == client {
            return Ok(());
        }
        Err(ServerError::ForeignHandle {
            handle: format!("{}", binding.service),
            client: format!("{client}"),
            backtrace: BackTrace::capture(),
        })
    }

    /// [`local`](Self::local) for a call that has no error to return: a
    /// foreign handle is a bug in the caller, and the alternative to stopping
    /// here is reading another device's memory.
    #[track_caller]
    fn expect_local(&self, binding: &BufferBinding) {
        if let Err(err) = self.local(binding) {
            panic!("{err}");
        }
    }

    /// Set the stream in which the current client is operating on.
    ///
    /// # Safety
    ///
    /// This is highly unsafe and should probably only be used by the CubeCL/Burn projects for now.
    pub unsafe fn set_stream(&mut self, stream_id: StreamId) {
        self.stream_id = Some(stream_id);
    }

    fn do_read(&self, descriptors: Vec<CopyDescriptor>) -> DynFut<Result<Vec<Bytes>, ServerError>> {
        if let Some(err) = descriptors
            .iter()
            .find_map(|descriptor| self.local(&descriptor.handle).err())
        {
            return Box::pin(core::future::ready(Err(err)));
        }
        let stream_id = self.stream_id();
        self.device
            .submit_blocking(move |server| server.read(descriptors, stream_id))
            .closed_as_error()
    }

    /// Given bindings, returns owned resources as bytes.
    pub fn read_async(
        &self,
        handles: Vec<Handle>,
    ) -> impl Future<Output = Result<Vec<Bytes>, ServerError>> + Send {
        let shapes = handles
            .iter()
            .map(|it| [it.size_in_used() as usize].into())
            .collect::<Vec<Shape>>();
        let descriptors = handles
            .into_iter()
            .zip(shapes)
            .map(|(handle, shape)| CopyDescriptor::new(handle.binding(), shape, [1].into(), 1))
            .collect();

        self.do_read(descriptors)
    }

    /// Given bindings, returns owned resources as bytes.
    ///
    /// # Errors
    ///
    /// Returns a [`ServerError`] if the read operation fails, or if a an error occurred on the
    /// compute server leading to the read.
    pub fn read(&self, handles: Vec<Handle>) -> Result<Vec<Bytes>, ServerError> {
        cubecl_environment::future::reader::read_sync(self.read_async(handles))
    }

    /// Given a binding, returns owned resource as bytes.
    pub fn read_one(&self, handle: Handle) -> Result<Bytes, ServerError> {
        Ok(cubecl_environment::future::reader::read_sync(self.read_async(vec![handle]))?.remove(0))
    }

    /// Given a binding, returns owned resource as bytes.
    ///
    /// # Remarks
    ///
    /// Panics if the read operation fails. Useful for tests.
    pub fn read_one_unchecked(&self, handle: Handle) -> Bytes {
        cubecl_environment::future::reader::read_sync(self.read_async(vec![handle]))
            .unwrap()
            .remove(0)
    }

    /// Given bindings, returns owned resources as bytes.
    pub fn read_tensor_async(
        &self,
        descriptors: Vec<CopyDescriptor>,
    ) -> impl Future<Output = Result<Vec<Bytes>, ServerError>> + Send {
        self.do_read(descriptors)
    }

    /// Given bindings, returns owned resources as bytes.
    ///
    /// The tensor must be in the same layout as created by the runtime, or more strict.
    /// Contiguous tensors are always fine, strided tensors are only ok if the stride is similar to
    /// the one created by the runtime (i.e. padded on only the last dimension). A way to check
    /// stride compatibility on the runtime will be added in the future.
    ///
    /// Also see [`Client::create_tensor`].
    ///
    /// # Errors
    ///
    /// Returns a [`ServerError`] if the read operation fails, or if a an error occurred on the
    /// compute server leading to the read.
    pub fn read_tensor(&self, descriptors: Vec<CopyDescriptor>) -> Result<Vec<Bytes>, ServerError> {
        cubecl_environment::future::reader::read_sync(self.read_tensor_async(descriptors))
    }

    /// Given a binding, returns owned resource as bytes.
    /// See [`Client::read_tensor`]
    pub fn read_one_tensor_async(
        &self,
        descriptor: CopyDescriptor,
    ) -> impl Future<Output = Result<Bytes, ServerError>> + Send {
        let fut = self.read_tensor_async(vec![descriptor]);

        async { Ok(fut.await?.remove(0)) }
    }

    /// Given a binding, returns owned resource as bytes.
    ///
    /// # Remarks
    ///
    /// Panics if the read operation fails.
    /// See [`Client::read_tensor`]
    pub fn read_one_unchecked_tensor(&self, descriptor: CopyDescriptor) -> Bytes {
        self.read_tensor(vec![descriptor])
            .expect("the read failed, use `read_one_tensor_async` to handle the error")
            .remove(0)
    }

    /// Reads the buffer `source` describes lazily.
    ///
    /// The returned [`Bytes`] only performs the device-to-host copy on first access (e.g. during
    /// serialization). This lets a large number of device tensors be serialized without
    /// materializing them all in host memory at once: drain the [`Bytes`] sequentially rather than
    /// holding them all alive.
    ///
    /// Until that first access the [`Bytes`] hold `source`'s handle, so [`Handle::can_mut`] is
    /// false for it and a caller that honours it does not write the buffer in place: the data
    /// read is the data as it was at this call.
    /// A zero-copy host read keeps holding the source until dropped or copied for mutation.
    #[cfg(not(target_family = "wasm"))]
    pub fn read_lazy(&self, source: CopyDescriptor<Handle>) -> Bytes {
        self.expect_local(&source.handle.clone().binding());
        lazy::LazyDeviceController::new(self.clone(), source).into_bytes()
    }

    /// Reads the buffer `source` describes lazily, async variant.
    ///
    /// On native targets the returned future is immediately ready and yields a lazy [`Bytes`]
    /// whose device-to-host copy is deferred to first access (see [`read_lazy`](Self::read_lazy)).
    ///
    /// # Errors
    ///
    /// Returns a [`ServerError`] if a an error occurred on the compute server leading to the read.
    /// A device fault is not detected here: the copy is deferred, so it surfaces as an error on
    /// first access to the returned [`Bytes`].
    #[cfg(not(target_family = "wasm"))]
    pub fn read_lazy_async(
        &self,
        source: CopyDescriptor<Handle>,
    ) -> impl Future<Output = Result<Bytes, ServerError>> + Send {
        let binding = source.handle.clone().binding();
        if let Err(err) = self.local(&binding) {
            return core::future::ready(Err(err));
        }
        let stream_id = self.stream_id();
        let checked = self
            .device
            .submit_blocking(move |server| server.check(vec![binding], stream_id))
            .closed_as_error();
        if let Err(err) = checked {
            return core::future::ready(Err(err));
        }
        let controller = lazy::LazyDeviceController::new(self.clone(), source);
        core::future::ready(Ok(controller.into_bytes()))
    }

    /// Reads the buffer `source` describes lazily, async variant.
    ///
    /// On `wasm` the deferred copy cannot run inside the synchronous access path, so awaiting
    /// performs the read eagerly and yields a materialized [`Bytes`]. Awaiting one tensor at a
    /// time still bounds peak host memory, which is the point of the lazy API.
    #[cfg(target_family = "wasm")]
    pub fn read_lazy_async(
        &self,
        source: CopyDescriptor<Handle>,
    ) -> impl Future<Output = Result<Bytes, ServerError>> + Send {
        self.read_one_tensor_async(source.binding())
    }

    /// Given a resource handle, returns the storage resource.
    pub fn get_resource<S: ServerStorage>(
        &self,
        handle: Handle,
    ) -> Result<ManagedResource<<S::Storage as ComputeStorage>::Resource>, ServerError> {
        let stream_id = self.stream_id();
        let binding = handle.binding();
        self.local(&binding)?;
        if !self.is_service::<S>() {
            return Err(ServerError::ServiceMismatch {
                client: format!("{}", self.service_id()),
                requested: String::from(core::any::type_name::<S>()),
                backtrace: BackTrace::capture(),
            });
        }

        self.device
            .submit_blocking(move |server| {
                let server = (server as &mut dyn Any)
                    .downcast_mut::<S>()
                    .expect("is_service passed, so this is the server's type");
                server.get_resource(binding, stream_id)
            })
            .closed_as_error()
    }

    fn do_create_from_slices(
        &self,
        descriptors: Vec<MemoryLayoutDescriptor>,
        slices: Vec<Vec<u8>>,
    ) -> Vec<MemoryLayout> {
        let stream_id = self.stream_id();
        let (handle_base, layouts) =
            self.utilities
                .layout_policy
                .apply(self.service_id(), stream_id, &descriptors);

        let descriptors = descriptors
            .into_iter()
            .zip(layouts.iter())
            .zip(slices)
            .map(|((desc, alloc), data)| {
                (
                    CopyDescriptor::new(
                        alloc.memory.clone().binding(),
                        desc.shape,
                        alloc.strides.clone(),
                        desc.elem_size,
                    ),
                    Bytes::from_bytes_vec(data.to_vec()),
                )
            })
            .collect::<Vec<_>>();

        let (size, memory) = (handle_base.size(), handle_base.memory);
        self.device.submit(move |server| {
            // Cannot write on memory that wasn't initialized. The error is attached to the
            // buffer and is reported at the next sync point.
            if server.initialize_memory(memory, size, stream_id).is_ok() {
                server.write(descriptors, stream_id);
            }
        });

        layouts
    }

    fn do_create(
        &self,
        descriptors: Vec<MemoryLayoutDescriptor>,
        data: Vec<Bytes>,
    ) -> Vec<MemoryLayout> {
        let stream_id = self.stream_id();
        let (handle_base, layouts) =
            self.utilities
                .layout_policy
                .apply(self.service_id(), stream_id, &descriptors);

        let descriptors = descriptors
            .into_iter()
            .zip(layouts.iter())
            .zip(data)
            .map(|((desc, layout), data)| {
                (
                    CopyDescriptor::new(
                        layout.memory.clone().binding(),
                        desc.shape,
                        layout.strides.clone(),
                        desc.elem_size,
                    ),
                    data,
                )
            })
            .collect::<Vec<_>>();

        let (size, memory) = (handle_base.size(), handle_base.memory);
        self.device.submit(move |server| {
            // Cannot write on memory that wasn't initialized. The error is attached to the
            // buffer and is reported at the next sync point.
            if server.initialize_memory(memory, size, stream_id).is_ok() {
                server.write(descriptors, stream_id);
            }
        });

        layouts
    }

    /// Returns a resource handle containing the given data.
    ///
    /// # Notes
    ///
    /// Prefer using the more efficient [`Self::create`] function.
    pub fn create_from_slice(&self, slice: &[u8]) -> Handle {
        let shape: Shape = [slice.len()].into();

        self.do_create_from_slices(
            vec![MemoryLayoutDescriptor::new(
                MemoryLayoutStrategy::Contiguous,
                shape,
                1,
            )],
            vec![slice.to_vec()],
        )
        .remove(0)
        .memory
    }

    /// Run `task` with this device to itself, so nothing else is scheduled
    /// against it for the duration.
    ///
    /// # Errors
    ///
    /// The device could not be taken exclusively — another holder has it, or
    /// its runner is gone. Nothing ran, so the caller may retry.
    pub fn exclusive<'a, Re: Send + 'static, F: FnOnce() -> Re + Send + 'a>(
        &'a self,
        task: F,
    ) -> Result<Re, ServerError> {
        // We then launch the task.
        self.device
            .exclusive(task)
            .map_err(|err| ServerError::Generic {
                reason: format!("{err:?}"),
                backtrace: BackTrace::capture(),
            })
    }

    /// Run `task` with every allocation it makes routed to the persistent
    /// pool, then restore the previous mode.
    ///
    /// Persistent slices are exact-fit and are not reclaimed by the ordinary
    /// sweep, which is what weights want: allocated once, alive for the
    /// process, and stable enough for a graph capture to record against.
    pub fn memory_persistent_allocation<
        'a,
        Re: Send,
        Input: Send,
        F: FnOnce(Input) -> Re + Send + 'a,
    >(
        &'a self,
        input: Input,
        task: F,
    ) -> Re {
        self.allocation_window(MemoryAllocationMode::Persistent, input, task)
    }

    /// Run `task` with every allocation it makes given its own device
    /// allocation outside every pool, returned to the driver once freed, then
    /// restore the previous mode.
    ///
    /// For buffers that exist for one measurement and nothing after it: they
    /// stay out of the pools' reservations and out of the statistics an
    /// adaptive pool sizes its pages from.
    pub fn memory_dedicated_allocation<
        'a,
        Re: Send,
        Input: Send,
        F: FnOnce(Input) -> Re + Send + 'a,
    >(
        &'a self,
        input: Input,
        task: F,
    ) -> Re {
        self.allocation_window(MemoryAllocationMode::Dedicated, input, task)
    }

    /// Open a window of `mode` on the current stream around `task`, and close
    /// it after. Private because `Auto` is what closes a window: the public
    /// entry points each name a mode that opens one.
    fn allocation_window<'a, Re: Send, Input: Send, F: FnOnce(Input) -> Re + Send + 'a>(
        &'a self,
        mode: MemoryAllocationMode,
        input: Input,
        task: F,
    ) -> Re {
        let stream_id = StreamId::current();

        self.device.submit(move |server| {
            server.allocation_mode(mode, stream_id);
        });

        // All tasks created on the same stream allocate in this mode.
        let output = task(input);

        self.device.submit(move |server| {
            server.allocation_mode(MemoryAllocationMode::Auto, stream_id);
        });

        output
    }

    /// Write `data` into an existing allocation, in place (same device pointer).
    ///
    /// This is how a captured [`Graph`]'s inputs are refreshed between replays:
    /// the graph records raw device pointers, so new input bytes must land in
    /// the very buffer the capture read from. Issue it from the capture stream
    /// (see the stream-ordering notes on [`Graph`]) so the write orders against
    /// the replays instead of racing them.
    ///
    /// Non-blocking: the write is enqueued on this client's current stream.
    pub fn write(&self, handle: &Handle, data: Bytes) {
        let stream_id = self.stream_id();
        let descriptor =
            CopyDescriptor::new(handle.clone().binding(), [data.len()].into(), [1].into(), 1);
        self.expect_local(&descriptor.handle);
        self.device.submit(move |server| {
            server.write(vec![(descriptor, data)], stream_id);
        });
    }

    /// Returns a resource handle containing the given [Bytes].
    pub fn create(&self, data: Bytes) -> Handle {
        let shape = [data.len()].into();

        self.do_create(
            vec![MemoryLayoutDescriptor::new(
                MemoryLayoutStrategy::Contiguous,
                shape,
                1,
            )],
            vec![data],
        )
        .remove(0)
        .memory
    }

    /// Given a resource and shape, stores it and returns the tensor handle and strides.
    /// This may or may not return contiguous strides. The layout is up to the runtime, and care
    /// should be taken when indexing.
    ///
    /// Currently the tensor may either be contiguous (most runtimes), or "pitched", to use the CUDA
    /// terminology. This means the last (contiguous) dimension is padded to fit a certain alignment,
    /// and the strides are adjusted accordingly. This can make memory accesses significantly faster
    /// since all rows are aligned to at least 16 bytes (the maximum load width), meaning the GPU
    /// can load as much data as possible in a single instruction. It may be aligned even more to
    /// also take cache lines into account.
    ///
    /// However, the stride must be taken into account when indexing and reading the tensor
    /// (also see [`Client::read_tensor`]).
    ///
    /// # Notes
    ///
    /// Prefer using [`Self::create_tensor`] for better performance.
    pub fn create_tensor_from_slice(
        &self,
        slice: &[u8],
        shape: Shape,
        elem_size: usize,
    ) -> MemoryLayout {
        self.do_create_from_slices(
            vec![MemoryLayoutDescriptor::new(
                MemoryLayoutStrategy::Optimized,
                shape,
                elem_size,
            )],
            vec![slice.to_vec()],
        )
        .remove(0)
    }

    /// Given a resource and shape, stores it and returns the tensor handle and strides.
    /// This may or may not return contiguous strides. The layout is up to the runtime, and care
    /// should be taken when indexing.
    ///
    /// Currently the tensor may either be contiguous (most runtimes), or "pitched", to use the CUDA
    /// terminology. This means the last (contiguous) dimension is padded to fit a certain alignment,
    /// and the strides are adjusted accordingly. This can make memory accesses significantly faster
    /// since all rows are aligned to at least 16 bytes (the maximum load width), meaning the GPU
    /// can load as much data as possible in a single instruction. It may be aligned even more to
    /// also take cache lines into account.
    ///
    /// However, the stride must be taken into account when indexing and reading the tensor
    /// (also see [`Client::read_tensor`]).
    pub fn create_tensor(&self, bytes: Bytes, shape: Shape, elem_size: usize) -> MemoryLayout {
        self.do_create(
            vec![MemoryLayoutDescriptor::new(
                MemoryLayoutStrategy::Optimized,
                shape,
                elem_size,
            )],
            vec![bytes],
        )
        .remove(0)
    }

    /// Reserves all `shapes` in a single storage buffer, copies the corresponding `data` into each
    /// handle, and returns the handles for them.
    /// See [`Client::create_tensor`]
    ///
    /// # Notes
    ///
    /// Prefer using [`Self::create_tensors`] for better performance.
    pub fn create_tensors_from_slices(
        &self,
        descriptors: Vec<(MemoryLayoutDescriptor, &[u8])>,
    ) -> Vec<MemoryLayout> {
        let mut data = Vec::with_capacity(descriptors.len());
        let mut descriptors_ = Vec::with_capacity(descriptors.len());
        for (a, b) in descriptors {
            data.push(b.to_vec());
            descriptors_.push(a);
        }

        self.do_create_from_slices(descriptors_, data)
    }

    /// Reserves all `shapes` in a single storage buffer, copies the corresponding `data` into each
    /// handle, and returns the handles for them.
    /// See [`Client::create_tensor`]
    pub fn create_tensors(
        &self,
        descriptors: Vec<(MemoryLayoutDescriptor, Bytes)>,
    ) -> Vec<MemoryLayout> {
        let (descriptors, data) = descriptors.into_iter().unzip();

        self.do_create(descriptors, data)
    }

    fn do_empty(&self, descriptors: Vec<MemoryLayoutDescriptor>) -> Vec<MemoryLayout> {
        let stream_id = self.stream_id();
        let (handle_base, layouts) =
            self.utilities
                .layout_policy
                .apply(self.service_id(), stream_id, &descriptors);

        let (size, memory) = (handle_base.size(), handle_base.memory);
        self.device.submit(move |server| {
            // The error is attached to the buffer and is reported at the next sync point.
            let _ = server.initialize_memory(memory, size, stream_id);
        });

        layouts
    }

    /// Reserves `size` bytes in the storage, and returns a handle over them.
    pub fn empty(&self, size: usize) -> Handle {
        let shape: Shape = [size].into();
        let descriptor = MemoryLayoutDescriptor::new(MemoryLayoutStrategy::Contiguous, shape, 1);
        self.do_empty(vec![descriptor]).remove(0).memory
    }

    /// Reserves `shape` in the storage, and returns a tensor handle for it.
    /// See [`Client::create_tensor`]
    pub fn empty_tensor(&self, shape: Shape, elem_size: usize) -> MemoryLayout {
        let descriptor =
            MemoryLayoutDescriptor::new(MemoryLayoutStrategy::Optimized, shape, elem_size);
        self.do_empty(vec![descriptor]).remove(0)
    }

    /// Reserves all `shapes` in a single storage buffer, and returns the handles for them.
    /// See [`Client::create_tensor`]
    pub fn empty_tensors(&self, descriptors: Vec<MemoryLayoutDescriptor>) -> Vec<MemoryLayout> {
        self.do_empty(descriptors)
    }

    /// Marks the given [Bytes] as being a staging buffer, maybe transferring it to pinned memory
    /// for faster data transfer with compute device.
    ///
    /// TODO: This blocks the compute queue, so it will drop the compute utilization.
    pub fn staging<'a, I>(&self, bytes: I, file_only: bool)
    where
        I: Iterator<Item = &'a mut Bytes>,
    {
        let has_staging = |b: &Bytes| match b.property() {
            AllocationProperty::Pinned => false,
            AllocationProperty::File => true,
            // A lazily device-backed buffer materializes on access and is staged (if needed)
            // by the backend write path, so don't force it into a host staging buffer here.
            AllocationProperty::Device => false,
            AllocationProperty::Native | AllocationProperty::Other => !file_only,
        };

        let mut to_be_updated = Vec::new();
        let sizes = bytes
            .filter_map(|b| match has_staging(b) {
                true => {
                    let len = b.len();
                    to_be_updated.push(b);
                    Some(len)
                }
                false => None,
            })
            .collect::<Vec<usize>>();

        if sizes.is_empty() {
            return;
        }

        let stream_id = self.stream_id();
        let sizes = sizes.to_vec();
        let stagings = self
            .device
            .submit_blocking(move |server| server.staging(&sizes, stream_id))
            .closed_as_error();

        let stagings = match stagings {
            Ok(val) => val,
            Err(_) => return,
        };

        to_be_updated
            .into_iter()
            .zip(stagings)
            .for_each(|(b, mut staging)| {
                b.copy_into(&mut staging);
                core::mem::swap(b, &mut staging);
            });
    }

    /// Whether kernels launched through this client can load, store and run
    /// atomics on memory `peer` [shared](Self::share_with_peers).
    pub fn can_access_peer(&self, peer: &Self) -> bool {
        let peer_device = peer.device.device_id();
        if peer.service_id().service != self.service_id().service
            || peer_device == self.device.device_id()
        {
            return false;
        }
        self.reaches_peer(peer_device)
    }

    /// `handle`, shared with the other devices of this runtime, which bind it
    /// through a `Peer` kernel parameter. The memory stays in place while the
    /// returned handle lives.
    ///
    /// Nothing orders a peer's accesses against this device's work: sync the
    /// writing device first, or hand off inside the kernels with system-scope
    /// atomics.
    ///
    /// # Errors
    ///
    /// [`ServerError::NoDeviceTransport`] on a runtime without peer access,
    /// [`ServerError::ForeignHandle`] for a handle of another client, and the
    /// failure the buffer carries.
    pub fn share_with_peers(&self, handle: &Handle) -> Result<Handle, ServerError> {
        let mut handle = handle.clone();
        let binding = handle.clone().binding();
        self.local(&binding)?;
        // Peer bindings add their own offsets to the allocation's address.
        let whole = BufferBinding {
            offset_start: None,
            offset_end: None,
            peer: None,
            ..binding
        };
        let pin = whole.memory.clone();
        let address = self
            .device
            .submit_blocking(move |server| server.peer_address(whole))
            .closed_as_error()?;
        handle.peer = Some(PeerMemory::new(pin, address, self.device.clone()));
        Ok(handle)
    }

    /// Transfer data from one client to another.
    ///
    /// `src` must be this client's. The bytes go device to device when both
    /// clients are of the same runtime and it has a collective transport;
    /// otherwise, and always across runtimes, they go through the host.
    ///
    /// On CUDA, transfers run on a communicator and stream of their own, so neither waits in
    /// NCCL's queue behind a collective; a stream [`sync_collective`](Self::sync_collective) made
    /// wait on one still does.
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(level = "trace", skip(self, src, dst_server))
    )]
    pub fn to_client(&mut self, src: Handle, dst_server: &Self) -> Handle {
        self.expect_local(&src.clone().binding());
        let shape = [src.size_in_used() as usize];
        let src_descriptor = src.copy_descriptor(shape.into(), [1].into(), 1);

        let same_runtime = dst_server.service_id().service == self.service_id().service;
        if self.has_device_transport() && same_runtime {
            self.to_client_tensor(src_descriptor, dst_server)
        } else {
            let alloc_desc = MemoryLayoutDescriptor::new(
                MemoryLayoutStrategy::Contiguous,
                src_descriptor.shape.clone(),
                src_descriptor.elem_size,
            );
            self.change_client_sync(src_descriptor, alloc_desc, dst_server)
                .memory
        }
    }

    /// Sets up the group over `device_ids` on every one of its devices, unless it already is.
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(level = "trace", skip(self, device_ids))
    )]
    pub fn ensure_init_collective(&self, device_ids: Vec<DeviceId>) {
        self.expect_device_transport(Collective::CommInit);
        // Two ranks on one device wait on its server thread for each other, forever.
        if let Some(repeated) = repeated_device(&device_ids) {
            panic!(
                "{repeated:?} appears twice among a collective's devices, which need one rank each"
            );
        }
        let comm_id = CommunicationId::from(device_ids.clone());
        if self.utilities.initialized_comms.read().contains(&comm_id) {
            return;
        }
        // Each member's setup waits for the others', so none may wait in turn on work queued
        // behind it, such as this caller's next part on its own device.
        let _order = PEER_ORDER.lock();
        if self.utilities.initialized_comms.read().contains(&comm_id) {
            return;
        }
        let members: Vec<Self> = device_ids
            .iter()
            .map(|device| (self.load_peer)(*device))
            .collect();
        for member in &members {
            let device_ids = device_ids.clone();
            member
                .device
                .submit(move |server| server.comm_init(device_ids).unwrap());
            member
                .utilities
                .initialized_comms
                .write()
                .insert(comm_id.clone());
        }
        for member in &members {
            member.device.flush_queue();
        }
    }

    /// Whether this runtime moves data between its devices itself. Without it, `to_client`
    /// copies through the host and the collectives refuse.
    pub fn has_device_transport(&self) -> bool {
        self.utilities.device_transport.is_some()
    }

    /// Panics on the caller when the runtime has no device transport.
    fn expect_device_transport(&self, operation: Collective) {
        // The server refuses too, but on the device thread, where the channel turns the panic into
        // a log line and the caller only sees a later read fail.
        if !self.has_device_transport() {
            let alternative = match operation {
                Collective::Send | Collective::Recv => "; `to_client` copies through the host",
                _ => "",
            };
            panic!(
                "Can't use `{operation}` on {}, which has no transport between its devices{alternative}",
                self.utilities.name
            );
        }
    }

    /// Wait on the communication stream.
    ///
    /// Call it once every device has queued its part of the `all_reduce` calls it waits for: a
    /// transfer from this device queued in between would wait on a part not queued yet. A
    /// [`ClientGroup`]'s collectives need none: each one's stream waits for it at once.
    #[cfg_attr(feature = "tracing", tracing::instrument(level = "trace", skip(self)))]
    pub fn sync_collective(&self) {
        if DeviceHandle::<dyn Server>::is_blocking() {
            panic!("Can't use `sync_collective` with a blocking device handle");
        }
        // Nothing was sent between devices, so there is nothing to wait for.
        if !self.has_device_transport() {
            return;
        }
        let stream_id = self.stream_id();

        self.device.submit(move |server| {
            // Logged rather than unwrapped: a panic on the server thread is
            // reduced to a log line by the channel's catch_unwind anyway, so
            // report deliberately instead of through a swallowed unwind.
            if let Err(err) = server.sync_collective(stream_id) {
                log::error!("sync_collective failed: {err}");
            }
        });

        // We don't actually need or want to sync the server here, but we need to make sure any
        // task enqueued on the communication channel is done.
        self.device.flush_queue();
    }

    /// Perform an `all_reduce` operation on the given devices.
    ///
    /// Every device has to queue the `all_reduce` calls over a group in one order. Queue each
    /// call on every device before the next: a device waiting in NCCL for its peers stops taking
    /// work after about a thousand calls, or as soon as it relocates memory, and the thread
    /// queueing them stops with it.
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(level = "trace", skip(self, src, dst, dtype, device_ids, op))
    )]
    pub fn all_reduce(
        &mut self,
        src: Handle,
        dst: Handle,
        dtype: ElemType,
        device_ids: Vec<DeviceId>,
        op: ReduceOperation,
    ) {
        let collective = Collective::AllReduce;
        let size = src.size_in_used();
        Self::expect_whole_elements(collective, dtype, size);
        let held = dst.size_in_used();
        assert!(
            held == size,
            "{collective}'s destination holds {held} bytes where its source holds {size}"
        );
        self.prepare_collective(collective, device_ids.clone());
        self.queue_all_reduce(
            src,
            dst,
            Reduction { dtype, op },
            device_ids,
            ComputeWait::AtSync,
        );
    }

    fn expect_whole_elements(collective: Collective, dtype: ElemType, size: u64) {
        assert!(
            size.is_multiple_of(dtype.size() as u64),
            "{collective} cannot cut {size} bytes into whole {dtype:?} elements"
        );
    }

    /// Checks `collective` can run from here, and sets up the group over `device_ids`.
    fn prepare_collective(&self, collective: Collective, device_ids: Vec<DeviceId>) {
        if DeviceHandle::<dyn Server>::is_blocking() {
            panic!("Can't use `{collective}` with a blocking device handle");
        }
        self.expect_device_transport(collective);
        self.ensure_init_collective(device_ids);
    }

    fn queue_all_reduce(
        &self,
        src: Handle,
        dst: Handle,
        reduction: Reduction,
        device_ids: Vec<DeviceId>,
        wait: ComputeWait,
    ) {
        let (src, dst) = (src.binding(), dst.binding());
        self.expect_local(&src);
        self.expect_local(&dst);
        self.queue_collective(Collective::AllReduce, move |server, stream_id| {
            server.all_reduce(src, dst, reduction, stream_id, device_ids, wait)
        });
    }

    fn queue_all_gather(&self, src: Handle, dst: Handle, device_ids: Vec<DeviceId>) {
        let (src, dst) = (src.binding(), dst.binding());
        self.expect_local(&src);
        self.expect_local(&dst);
        self.queue_collective(Collective::AllGather, move |server, stream_id| {
            server.all_gather(src, dst, stream_id, device_ids)
        });
    }

    fn queue_reduce_scatter(
        &self,
        src: Handle,
        dst: Handle,
        reduction: Reduction,
        device_ids: Vec<DeviceId>,
    ) {
        let (src, dst) = (src.binding(), dst.binding());
        self.expect_local(&src);
        self.expect_local(&dst);
        self.queue_collective(Collective::ReduceScatter, move |server, stream_id| {
            server.reduce_scatter(src, dst, reduction, stream_id, device_ids)
        });
    }

    fn queue_broadcast(
        &self,
        src: Option<Handle>,
        dst: Handle,
        root: DeviceId,
        device_ids: Vec<DeviceId>,
    ) {
        let (src, dst) = (src.map(Handle::binding), dst.binding());
        src.iter()
            .chain([&dst])
            .for_each(|binding| self.expect_local(binding));
        self.queue_collective(Collective::Broadcast, move |server, stream_id| {
            server.broadcast(src, dst, stream_id, root, device_ids)
        });
    }

    fn queue_all_to_all(&self, src: Handle, dst: Handle, device_ids: Vec<DeviceId>) {
        let (src, dst) = (src.binding(), dst.binding());
        self.expect_local(&src);
        self.expect_local(&dst);
        self.queue_collective(Collective::AllToAll, move |server, stream_id| {
            server.all_to_all(src, dst, stream_id, device_ids)
        });
    }

    /// Queues this device's part of `collective`.
    fn queue_collective(
        &self,
        collective: Collective,
        part: impl FnOnce(&mut dyn Server, StreamId) -> Result<(), ServerError> + Send + 'static,
    ) {
        let stream_id = self.stream_id();
        self.device.submit(move |server| {
            // The tainted destination is the report; an unwrap would only become a warning here.
            if let Err(err) = part(server, stream_id) {
                log::error!(
                    "{collective} failed, so the peers that queued their part wait in it, and the \
                     destination carries the failure: {err}"
                );
            }
        });
    }

    /// Transfer data from one client to another
    ///
    /// Make sure the source description can be read in a contiguous manner.
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(level = "trace", skip(self, src_descriptor, dst_server))
    )]
    pub fn to_client_tensor(
        &mut self,
        src_descriptor: CopyDescriptor,
        dst_server: &Self,
    ) -> Handle {
        self.expect_device_transport(Collective::Send);
        self.expect_local(&src_descriptor.handle);
        let stream_id_src = self.stream_id();
        let stream_id_dst = dst_server.stream_id();

        let device_id_src = self.device.device_id();
        let device_id_dst = dst_server.device.device_id();

        let dst_server = dst_server.clone();
        let handle = Handle::new(
            dst_server.service_id(),
            stream_id_dst,
            src_descriptor.handle.size_in_used(),
        );
        let handle_cloned = handle.clone();

        // NCCL pairs sends and recvs in the order each device queues them.
        let _order = PEER_ORDER.lock();

        self.device.submit(move |server_src| {
            // A refused send has no local buffer to answer for, so the log is
            // the whole local report. The peer's posted recv is left waiting
            // on its communication stream — the recv cannot be recalled from
            // here, and cross-device failure propagation needs a design pass
            // of its own — so the wedge is named loudly rather than hidden
            // behind a swallowed unwrap.
            if let Err(err) = server_src.send(src_descriptor, stream_id_src, device_id_dst) {
                log::error!(
                    "send to {device_id_dst:?} failed; the peer's recv is left waiting: {err}"
                );
            }
        });

        dst_server.device.submit(move |server_dst| {
            // A failed recv taints the destination handle, so the read that
            // consumes this transfer fails on the cause.
            if let Err(err) = server_dst.recv(handle_cloned, stream_id_dst, device_id_src) {
                log::error!(
                    "recv from {device_id_src:?} failed; the destination carries the failure: {err}"
                );
            }
        });

        // On a pair's first transfer, the send and the recv each wait in the join for the other, so
        // neither may sit in a queue behind work that waits on this thread.
        self.device.flush_queue();
        dst_server.device.flush_queue();

        handle
    }

    #[track_caller]
    #[cfg_attr(feature = "tracing", tracing::instrument(level="trace",
        skip(self, kernel, bindings),
        fields(
            kernel.name = %kernel.name(),
            kernel.id = %kernel.id(),
        )
    ))]
    unsafe fn launch_inner(
        &self,
        kernel: Box<dyn CubeKernel>,
        count: CubeCount,
        mut bindings: KernelArguments,
        stream_id: StreamId,
    ) {
        // No work, and some drivers reject a zero grid dim.
        if let CubeCount::Static(x, y, z) = &count
            && (*x == 0 || *y == 0 || *z == 0)
        {
            return;
        }
        if let CubeCount::Dynamic(binding) = &count {
            self.expect_local(binding);
        }
        // A kernel with a `Peer` parameter may wait on another device, so it is
        // flushed now: a host blocked on that device would never flush it.
        let _reach_device_now = bindings
            .peers()
            .next()
            .is_some()
            .then(|| FlushOnDrop(&self.device));
        if bindings.peers().next().is_some() {
            let resources = core::mem::take(&mut bindings.resources);
            bindings.resources = resources
                .into_iter()
                .map(|resource| match resource {
                    KernelResource::Peer(peer) => self.bind_peer(peer),
                    resource => resource,
                })
                .collect();
        }
        // Another device's memory binds only through a `Peer` parameter.
        for resource in &bindings.resources {
            if let Some(binding) = resource.local_binding() {
                self.expect_local(binding);
            }
        }

        crate::launched::note(|| kernel.id());

        // Decided here, where the launch is issued, from the stream it goes
        // out on: the server receives the verdict, not what decided it.
        let launch_mode = crate::execution::LaunchMode::new(self.service_stream());
        // So is where its kernels count: the device runs it later, and an
        // override closing in between must not change that.
        let issued = crate::execution::IssuedRecorder::new();

        // A discarded launch runs nothing to time, and a backend timing windows by the
        // timestamps its passes write reports a window around one as never measured.
        let timed = !launch_mode.discards_launch();
        let level = self.utilities.logger.profile_level().filter(|_| timed);

        // Before the submit, on the issuing thread: this is the last point at
        // which the caller's own context still exists, and attributing a
        // launch to what caused it is the whole reason the hook is here rather
        // than beside the logger's aggregation.
        if crate::logging::is_observing() {
            crate::logging::notify_launch(kernel.name());
        }

        // An observer asking for timing gets the profiled path even with the
        // profiling logger off — the two are separate readers of the same
        // measurement, and making one depend on the other's configuration
        // would mean a caller could not time launches without also logging
        // them somewhere it did not choose.
        let observed_timing = timed && crate::logging::timing_wanted();

        match level {
            None | Some(ProfileLevel::ExecutionOnly) if !observed_timing => {
                let utilities = self.utilities.clone();
                self.device.submit(move |state| {
                    let execution_info = if matches!(level, Some(ProfileLevel::ExecutionOnly)) {
                        Some(profile_label(kernel.name(), &kernel.id()))
                    } else {
                        None
                    };

                    issued.apply(|| unsafe {
                        state.launch(kernel, count, bindings, stream_id, launch_mode)
                    });

                    if let Some(info) = execution_info {
                        utilities.logger.register_execution(info);
                    }
                });
            }
            level => {
                let name = kernel.name();
                let kernel_id = kernel.id();
                let context = self.device.clone();
                // The arguments travel through a slot the profiled closure
                // empties, because a profile can be refused — a graph capture
                // window refuses one on the spot — and a refusal must hand the
                // launch back: dropping a kernel because its measurement could
                // not start would turn a missing timing into a missing
                // computation.
                let slot = Arc::new(cubecl_environment::sync::Mutex::new(Some((
                    kernel,
                    count.clone(),
                    bindings,
                ))));
                let to_launch = slot.clone();
                let issued_profiled = issued.clone();
                let profiled = self.profile_opened(
                    WindowOpens::AtLaunch,
                    move || {
                        let (kernel, count, bindings) = to_launch
                            .lock()
                            .take()
                            .expect("filled right above, emptied only here");
                        context
                            .submit_blocking(move |state| {
                                issued_profiled.apply(|| unsafe {
                                    state.launch(kernel, count, bindings, stream_id, launch_mode)
                                })
                            })
                            .unwrap_or_resume()
                    },
                    name,
                );
                let profile = match profiled {
                    Ok(((), profile)) => profile,
                    Err(err) => {
                        // The logger's timing levels opted into profiling and
                        // keep their loud failure. Only the observer's timing
                        // degrades: it asked for a measurement, and a refused
                        // measurement must not take the launch down with it.
                        if !matches!(level, None | Some(ProfileLevel::ExecutionOnly)) {
                            panic!("{err:?}");
                        }
                        match slot.lock().take() {
                            // The refusal came before the closure ran, so the
                            // kernel was never submitted. Launch it the way an
                            // unobserved run would have.
                            Some((kernel, count, bindings)) => {
                                let utilities = self.utilities.clone();
                                let kernel_id = kernel.id();
                                self.device.submit(move |state| {
                                    issued.apply(|| unsafe {
                                        state.launch(
                                            kernel,
                                            count,
                                            bindings,
                                            stream_id,
                                            launch_mode,
                                        )
                                    });
                                    if matches!(level, Some(ProfileLevel::ExecutionOnly)) {
                                        let info = profile_label(name, &kernel_id);
                                        utilities.logger.register_execution(info);
                                    }
                                });
                            }
                            // The closure ran, so the kernel was submitted;
                            // only its measurement was lost.
                            None => {
                                if matches!(level, Some(ProfileLevel::ExecutionOnly)) {
                                    let info = profile_label(name, &kernel_id);
                                    self.utilities.logger.register_execution(info);
                                }
                            }
                        }
                        log::warn!(
                            "Skipped timing a launch of `{name}` for its observer: the profile was refused ({err:?})"
                        );
                        return;
                    }
                };
                // The observer alone: it takes the measurement unread, so the
                // kernels around this one keep running back to back. An observer
                // does not change what the logger writes, and `ExecutionOnly` is
                // documented as the kernels that ran without their timings, so
                // it logs the execution and never the profile.
                if observed_timing && matches!(level, None | Some(ProfileLevel::ExecutionOnly)) {
                    crate::logging::notify_profiled(name, profile);
                    if matches!(level, Some(ProfileLevel::ExecutionOnly)) {
                        let info = profile_label(name, &kernel_id);
                        self.utilities.logger.register_execution(info);
                    }
                    return;
                }
                // Both read this measurement, and a measurement is read once.
                // The observer is told first because resolving consumes it: the
                // logger's copy is the one that can be deferred, an observer's
                // cannot be recovered afterwards.
                let profile = if observed_timing {
                    // The observer asked to keep its measurements and cannot:
                    // the logger reads this one, so the observer is told a
                    // duration and its kernels stop overlapping.
                    crate::logging::warn_logger_takes_deferred_measurements();
                    // Comes back already resolved rather than measured again:
                    // the logger and the observer are two readers of one
                    // measurement, and a second would not be the same launch.
                    crate::logging::read_and_notify_timed(name, profile)
                } else {
                    profile
                };
                // Every level left times its launches: the ones that don't
                // either never took this path or returned above.
                let info = match level {
                    Some(ProfileLevel::Full) => {
                        format!("{name}: {kernel_id} CubeCount {count:?}")
                    }
                    _ => profile_label(name, &kernel_id),
                };
                self.utilities.logger.register_profiled(info, profile);
            }
        }
    }

    /// Launches the `kernel` with the given `bindings`.
    #[track_caller]
    pub fn launch(&self, kernel: Box<dyn CubeKernel>, count: CubeCount, bindings: KernelArguments) {
        unsafe { self.launch_inner(kernel, count, bindings, self.stream_id()) }
    }

    /// Whether the bytes behind `handles` can be trusted, right now and with
    /// no barrier: the claim check a read makes, without the read. One lookup
    /// per handle, so a fusion layer or an autotuner can recover per tensor
    /// instead of tearing down a device.
    ///
    /// Instant means enqueue-time failures only — a compile or binding
    /// failure is visible here immediately, a device fault is not until the
    /// queue drains. [`sync_buffers`](Self::sync_buffers) is the complete
    /// answer; [`read_one`](Self::read_one) is that plus the copy.
    ///
    /// # Errors
    ///
    /// [`ServerError::Several`] naming every failure these buffers carry, each
    /// once however many carry it. The bytes are gone, so there is nothing to
    /// retry: this is the answer, not a hint.
    pub fn check<'a>(
        &self,
        handles: impl IntoIterator<Item = &'a Handle>,
    ) -> Result<(), ServerError> {
        let bindings = self.bindings(handles)?;
        let stream_id = self.stream_id();
        self.device
            .submit_blocking(move |server| server.check(bindings, stream_id))
            .closed_as_error()
    }

    /// Flush all outstanding commands.
    pub fn flush(&self) -> Result<(), ServerError> {
        let stream_id = self.stream_id();

        self.device
            .submit_blocking(move |server| server.flush(stream_id))
            .closed_as_error()
    }

    /// Compile every kernel queued for compilation (see
    /// [`Server::compile_queued`]), before the work submitted after it.
    ///
    /// Every measurement starts with it — a tune, a throughput probe — so a
    /// queue a `CompileOnly` override left is not timed as part of the first
    /// launch measured.
    pub fn compile_queued(&self) {
        self.device.submit(move |server| server.compile_queued());
    }

    /// Prepare this client's stream for a graph capture (see
    /// [`Server::graph_prepare`]). Call this **before** the warmup run, then
    /// [`start_capture`](Self::start_capture) around the run to record.
    pub fn graph_prepare(&self) -> Result<(), ServerError> {
        let stream_id = self.stream_id();
        self.device
            .submit_blocking(move |server| server.graph_prepare(stream_id))
            .closed_as_error()
    }

    /// Begin recording launches on this client's stream into a graph rather
    /// than executing them (see [`Server::begin_capture`]). Pin the
    /// client to a dedicated stream with [`set_stream`](Self::set_stream), then
    /// [`graph_prepare`](Self::graph_prepare) and warm up first.
    ///
    /// Between this and [`stop_capture`](Self::stop_capture) the window records
    /// launches and nothing else: reading, syncing or profiling the stream is
    /// refused, and so is writing to a handle — a recorded graph cannot carry a
    /// host copy, so feed fresh inputs by writing *between* replays instead. A
    /// refused write is reported late, by failing `stop_capture`, rather than
    /// handing back a graph that silently skips it. Nothing is allocated inside
    /// the window: a request the pools cannot serve from what the warmup run
    /// left fails the capture, which is what the warmup run exists to avoid.
    ///
    /// Returns an error on backends without graph support.
    pub fn start_capture(&self) -> Result<(), ServerError> {
        let stream_id = self.stream_id();
        self.device
            .submit_blocking(move |server| server.begin_capture(stream_id))
            .closed_as_error()
    }

    /// Whether this client's stream is capturing a graph: from
    /// [`graph_prepare`](Self::graph_prepare), through the warmup run and the recorded one, until
    /// the capture ends. It ends with [`stop_capture`](Self::stop_capture), whether the window
    /// opened or the capture was only prepared, and also when another logical stream sharing
    /// the same backend stream stops it, or when opening the window fails once
    /// [`start_capture`](Self::start_capture) is accepted. A `start_capture` refused up front,
    /// e.g. while a capture already records, leaves the capture as it was. Always `false` on a
    /// backend without graph support.
    ///
    /// Answered without reaching the device thread, so code whose buffer decisions have to
    /// match between the warmup and the recording can ask before every launch.
    pub fn is_capturing(&self) -> bool {
        let captures = &self.utilities.captures;
        // The stream id costs more than the check, and no capture under way answers already.
        captures.any_active() && captures.is_capturing(self.stream_id())
    }

    /// Stop recording and return the captured graph, ready to
    /// [`replay`](Graph::replay).
    pub fn stop_capture(&self) -> Result<Graph, ServerError> {
        let stream_id = self.stream_id();
        let id = self
            .device
            .submit_blocking(move |server| server.end_capture(stream_id))
            .closed_as_error()?;

        Ok(Graph {
            inner: Arc::new(GraphHandle {
                id,
                device: self.device.clone(),
                stream_id,
            }),
        })
    }

    /// Wait for the completion of every task in the server.
    ///
    /// The barrier alone, which also reports a device fault — the only failure
    /// left that no buffer can report. A launch failure is not this sync's to
    /// report: it lives on the buffers the launch never wrote and surfaces on
    /// any read, [`check`](Self::check) or
    /// [`sync_buffers`](Self::sync_buffers) of those.
    pub fn sync(&self) -> DynFut<Result<(), ServerError>> {
        self.sync_buffers([])
    }

    /// The barrier, and then an answer for `handles`.
    ///
    /// [`sync`](Self::sync) first, so a device fault counts, and then the
    /// claim check a read would have made — a read without the read, for the
    /// caller that needs to know its work produced something trustworthy and
    /// does not want to pull it to the host to find out.
    ///
    /// # Errors
    ///
    /// The device fault the barrier found, or [`ServerError::Several`] naming
    /// every failure these buffers carry.
    pub fn sync_buffers<'a>(
        &self,
        handles: impl IntoIterator<Item = &'a Handle>,
    ) -> DynFut<Result<(), ServerError>> {
        let stream_id = self.stream_id();
        let bindings = match self.bindings(handles) {
            Ok(bindings) => bindings,
            Err(err) => return Box::pin(core::future::ready(Err(err))),
        };

        let fut = self
            .device
            .submit_blocking(move |server| server.sync(bindings, stream_id))
            .closed_as_error();

        self.utilities.logger.profile_summary();

        fut
    }

    /// The bindings `handles` name, which is what crosses to the device
    /// thread: a `Handle` borrows, and the closure that answers for it runs
    /// somewhere else.
    fn bindings<'a>(
        &self,
        handles: impl IntoIterator<Item = &'a Handle>,
    ) -> Result<Vec<BufferBinding>, ServerError> {
        handles
            .into_iter()
            .map(|handle| {
                let binding = handle.clone().binding();
                self.local(&binding)?;
                Ok(binding)
            })
            .collect()
    }

    /// Get the features supported by the compute server.
    pub fn properties(&self) -> &DeviceProperties {
        &self.utilities.properties
    }

    /// Get the features supported by the compute server.
    pub fn features(&self) -> &Features {
        &self.utilities.properties.features
    }

    /// Which hardware this device is: what a measurement on it holds for.
    pub fn hardware_identity(&self) -> HardwareIdentity {
        HardwareIdentity::new(self.name(), self.properties())
    }

    /// The device properties, shared: what a kernel keeps to expand itself
    /// on the device thread without holding the client.
    pub fn properties_shared(&self) -> Arc<DeviceProperties> {
        self.utilities.properties.clone()
    }

    /// What the target this client compiles for guarantees about its own
    /// instructions, resolved once when the device came up.
    pub fn target_properties(&self) -> &TargetProperties {
        &self.utilities.target_properties
    }

    /// The target properties, shared: the other half of what a kernel keeps to
    /// expand itself on the device thread without naming a runtime.
    ///
    /// Cloning this is one atomic increment, which is why the generated launch
    /// functions can afford to do it per launch where calling
    /// [`Runtime::target_properties`] again would not be.
    ///
    /// [`Runtime::target_properties`]: crate::runtime::Runtime::target_properties
    pub fn target_properties_shared(&self) -> Arc<TargetProperties> {
        self.utilities.target_properties.clone()
    }

    /// Everything the memory of `scope` holds, stream by stream: each pool's
    /// shape, usage and high-water marks. [`MemoryReport::usage`] sums them.
    ///
    /// Pools are per stream: a plan measured for a workload reads
    /// [`CurrentStream`](MemoryScope::CurrentStream), the stream that runs it,
    /// and a caller asking how much the device holds reads
    /// [`Device`](MemoryScope::Device).
    pub fn memory_report(&self, scope: MemoryScope) -> MemoryReport {
        let stream_id = self.stream_id();
        self.device
            .submit_blocking(move |server| {
                let streams = match scope {
                    MemoryScope::Device => server.stream_ids(),
                    MemoryScope::CurrentStream => Vec::from([stream_id]),
                };
                MemoryReport {
                    streams: streams
                        .into_iter()
                        .filter_map(|id| server.memory_report(id))
                        .collect(),
                }
            })
            .unwrap_or_resume()
    }

    /// Write a snapshot of the device's [memory report](Self::memory_report),
    /// every stream of it, to the environment's records under `label`.
    /// Nothing is read when the environment records nothing.
    pub fn record_memory(&self, label: &str) {
        if !cubecl_environment::records::enabled() {
            return;
        }
        let record = crate::memory_management::MemoryRecord {
            label: label.into(),
            report: self.memory_report(MemoryScope::Device),
        };
        cubecl_environment::records::write(
            cubecl_environment::records::RecordEffect::Observed,
            &record,
        );
    }

    /// Change the memory allocation mode.
    ///
    /// # Safety
    ///
    /// This function isn't thread safe and might create memory leaks.
    pub unsafe fn allocation_mode(&self, mode: MemoryAllocationMode) {
        let stream_id = self.stream_id();
        self.device
            .submit(move |server| server.allocation_mode(mode, stream_id));
    }

    /// Ask the client to release memory that it can release.
    ///
    /// Nb: Results will vary on what the memory allocator deems beneficial,
    /// so it's not guaranteed any memory is freed.
    ///
    /// # Errors
    ///
    /// Refused while a stream records a graph: releasing memory waits on the
    /// device, and a wait on a stream that records aborts its capture.
    pub fn memory_cleanup(&self) -> Result<(), ServerError> {
        self.device
            .submit_blocking(move |server| {
                server
                    .stream_ids()
                    .into_iter()
                    .try_for_each(|id| server.memory_cleanup(id))
            })
            .closed_as_error()
    }

    /// Open a profiling window at the current position of the calling stream.
    ///
    /// Prefer the bracketed [`profile`](Self::profile), which also holds the
    /// device for the closure. This pair is for a caller that cannot bracket the
    /// work in a closure — a lazy queue drained on another thread, say — and
    /// only knows *when* on the stream its window opens and closes.
    ///
    /// The window keeps the stream it was opened on, and
    /// [`profile_end`](Self::profile_end) closes it there whichever thread
    /// calls it. Nothing keeps other streams' work out of the window.
    ///
    /// An open window costs something on every backend and stays open until it
    /// is ended or [abandoned](Self::profile_abandon), so a caller that bails
    /// out between the two calls has to abandon it.
    pub fn profile_start(&self) -> Result<ProfileWindow, ProfileError> {
        let stream_id = self.stream_id();
        let token = self
            .device
            .submit_blocking(move |server| server.start_profile(stream_id))
            .closed_as_error()
            .map_err(|err| ProfileError::from(&err))?;
        Ok(ProfileWindow { stream_id, token })
    }

    /// Close `window` at the current position of the stream it was opened on.
    pub fn profile_end(&self, window: ProfileWindow) -> Result<ProfileDuration, ProfileError> {
        let ProfileWindow { stream_id, token } = window;
        self.device
            .submit_blocking(move |server| server.end_profile(stream_id, token))
            .closed_as_error()
    }

    /// Drop `window` without measuring it, for a caller that will never reach
    /// [`profile_end`](Self::profile_end), such as an error path between the
    /// two calls.
    ///
    /// Does not wait for the server to drop it, but does flush, because this
    /// is usually a caller's last word: an abandon left sitting in the queue
    /// holds the window open for exactly as long as it is the only thing in
    /// there, which is the case it exists for.
    pub fn profile_abandon(&self, window: ProfileWindow) {
        let ProfileWindow { stream_id, token } = window;
        self.device
            .submit(move |server| server.abandon_profile(stream_id, token));
        self.device.flush_queue();
    }

    /// Measure the execution time of some inner operations.
    #[track_caller]
    pub fn profile<O: Send + 'static>(
        &self,
        func: impl FnOnce() -> O + Send,
        func_name: &str,
    ) -> Result<(O, ProfileDuration), ProfileError> {
        self.profile_opened(WindowOpens::Now, func, func_name)
    }

    /// [`profile`](Self::profile), its window opened where `opens` says.
    #[track_caller]
    fn profile_opened<O: Send + 'static>(
        &self,
        opens: WindowOpens,
        func: impl FnOnce() -> O + Send,
        #[allow(unused)] func_name: &str,
    ) -> Result<(O, ProfileDuration), ProfileError> {
        // Get the outer caller. For execute() this points straight to the
        // cube kernel. For general profiling it points to whoever calls profile.
        #[cfg(feature = "profile-tracy")]
        let location = std::panic::Location::caller();

        // Make a CPU span. If the server has system profiling this is all you need.
        #[cfg(feature = "profile-tracy")]
        let _span = tracy_client::Client::running().unwrap().span_alloc(
            None,
            func_name,
            location.file(),
            location.line(),
            0,
        );

        let stream_id = self.stream_id();

        #[cfg(feature = "profile-tracy")]
        let gpu_span = if self.utilities.properties.timing_method == TimingMethod::Device {
            let gpu_span = self
                .utilities
                .gpu_client
                .span_alloc(func_name, "profile", location.file(), location.line())
                .unwrap();
            Some(gpu_span)
        } else {
            None
        };

        let device = self.device.clone();
        #[allow(unused_mut, reason = "Used in profile-tracy")]
        let mut result = self
            .device
            .exclusive(move || {
                // We first get mut access to the server to create a token.
                // Then we free to server, since it's going to be accessed in `func()`.
                let token = match device.submit_blocking(move |server| match opens {
                    WindowOpens::Now => server.start_profile(stream_id),
                    WindowOpens::AtLaunch => server.start_profile_at_launch(stream_id),
                }) {
                    Ok(token) => match token {
                        Ok(token) => token,
                        Err(err) => return Err(err),
                    },
                    Err(err) => {
                        return Err(ServerError::Generic {
                            reason: alloc::format!(
                                "Can't start profiling because of a call error: {err:?}"
                            ),
                            backtrace: BackTrace::capture(),
                        });
                    }
                };

                // We execute `func()` which will recursibly access the server.
                let out = func();

                // Finally we get the result from the token.
                let result = device
                    .submit_blocking(move |server| {
                        let mut result = server.end_profile(stream_id, token);

                        match result {
                            Ok(result) => Ok((out, result)),
                            Err(err) => Err(err),
                        }
                    })
                    .closed_as_error();

                Ok(result)
            })
            .closed_as_error()
            .map_err(|err| ProfileError::from(&err))?;

        #[cfg(feature = "profile-tracy")]
        if let Some(mut gpu_span) = gpu_span {
            gpu_span.end_zone();
            let epoch = self.utilities.epoch_time;
            // Add in the work to upload the timestamp data.
            result = result.map(|(o, result)| {
                (
                    o,
                    ProfileDuration::new(
                        alloc::boxed::Box::pin(async move {
                            let ticks = result.resolve().await;
                            // A window that carried no measurement has no span
                            // to place: `resolve` answers `None` rather than a
                            // zero so nothing reports it as an instant at the
                            // epoch.
                            if let Some(ticks) = &ticks {
                                let start_duration =
                                    ticks.start_duration_since(epoch).as_nanos() as i64;
                                let end_duration =
                                    ticks.end_duration_since(epoch).as_nanos() as i64;
                                gpu_span.upload_timestamp_start(start_duration);
                                gpu_span.upload_timestamp_end(end_duration);
                            }
                            ticks
                        }),
                        TimingMethod::Device,
                    ),
                )
            });
        }

        result
    }

    /// Transfer data from one client to another
    #[cfg_attr(
        feature = "tracing",
        tracing::instrument(
            level = "trace",
            skip(self, src_descriptor, alloc_descriptor, dst_server)
        )
    )]
    fn change_client_sync(
        &self,
        src_descriptor: CopyDescriptor,
        alloc_descriptor: MemoryLayoutDescriptor,
        dst_server: &Self,
    ) -> MemoryLayout {
        let shape = src_descriptor.shape.clone();
        let elem_size = src_descriptor.elem_size;
        let stream_id_src = self.stream_id();
        let stream_id_dst = dst_server.stream_id();

        let read = self
            .device
            .submit_blocking(move |server| server.read(vec![src_descriptor], stream_id_src))
            .closed_as_error();

        let mut data = cubecl_environment::future::block_on(read).unwrap();

        // The allocation belongs to the destination: it is initialized and
        // written there, so it takes that device's layout policy, stream and
        // `ServiceId`. Stamping it from `self` would hand back a handle the
        // destination refuses as foreign.
        let (handle_base, mut layouts) = dst_server.utilities.layout_policy.apply(
            dst_server.service_id(),
            stream_id_dst,
            &[alloc_descriptor],
        );
        let alloc = layouts.remove(0);

        let desc_descriptor = CopyDescriptor {
            handle: handle_base.clone().binding(),
            shape,
            strides: alloc.strides.clone(),
            elem_size,
        };

        let (size, memory) = (handle_base.size(), handle_base.memory);
        dst_server.device.submit(move |server| {
            // Cannot write on memory that wasn't initialized. The error is attached to the
            // buffer and is reported at the next sync point.
            if server
                .initialize_memory(memory, size, stream_id_dst)
                .is_ok()
            {
                server.write(vec![(desc_descriptor, data.remove(0))], stream_id_dst)
            }
        });

        alloc
    }

    /// Returns all vector sizes that are useful to perform optimal IO operation on the given element.
    pub fn io_optimized_vector_sizes(
        &self,
        size: usize,
    ) -> impl Iterator<Item = VectorSize> + Clone {
        self.properties().io_optimized_vector_sizes(size)
    }

    /// Calculates the maximum throughput of the device given the given config (like tensor core with certain sizes and dtypes, or just arithmetic by dtype)
    ///
    /// `probe` runs on the device runner thread with the device to itself,
    /// since one sharing it measures its share rather than the peak. A cached
    /// answer takes neither.
    ///
    /// # Errors
    ///
    /// Whatever `probe` reports, or [`Launch`](ThroughputError::Launch) where
    /// the device could not be taken.
    pub fn measure_throughput(
        &self,
        key: ThroughputKey,
        probe: impl FnOnce() -> Result<ThroughputValue, ThroughputError> + Send,
    ) -> Result<ThroughputValue, ThroughputError> {
        let cache = ThroughputCache::get_for_device(self.name(), self.properties());
        let mut throughputs = ThroughputBenchmarker::new(cache);

        if let Some(value) = throughputs.cached(key) {
            return Ok(value);
        }

        // Kernels queued for compilation compile now, together, rather than in the probe's
        // first launch, inside the time it measures.
        self.compile_queued();
        // Asked again inside: another thread may have answered while this one queued.
        self.exclusive(move || throughputs.measure(key, probe))
            .unwrap_or(Err(ThroughputError::Launch))
    }
}

fn profile_label(name: &'static str, kernel_id: &KernelId) -> String {
    let base = type_name_format(name, TypeNameFormatLevel::Balanced);
    kernel_id.entrypoint_name(&base)
}

/// A blocking call whose answer is already a [`ServerError`] result reads a service that was
/// closed as one more error rather than a panic: a client still issuing work as the process
/// exits ([`DeviceHandle::close`]) is told the device is gone. Any other failure, a panic in the
/// task or a runner that is gone, is re-raised, as [`CallResultExt::unwrap_or_resume`] does.
trait ClosedAsError {
    type Answer;

    fn closed_as_error(self) -> Self::Answer;
}

/// The error a call on a closed service answers with.
fn device_closed() -> ServerError {
    ServerError::Generic {
        reason: "the device was closed, as the process exits".into(),
        backtrace: BackTrace::capture(),
    }
}

impl<R, E: From<ServerError>> ClosedAsError for Result<Result<R, E>, CallError> {
    type Answer = Result<R, E>;

    fn closed_as_error(self) -> Self::Answer {
        match self {
            Ok(answer) => answer,
            Err(error) if error.is_closed() => Err(device_closed().into()),
            Err(error) => error.resume(),
        }
    }
}

impl<R: Send + 'static> ClosedAsError for Result<DynFut<Result<R, ServerError>>, CallError> {
    type Answer = DynFut<Result<R, ServerError>>;

    fn closed_as_error(self) -> Self::Answer {
        match self {
            Ok(answer) => answer,
            Err(error) if error.is_closed() => Box::pin(core::future::ready(Err(device_closed()))),
            Err(error) => error.resume(),
        }
    }
}