Struct CountingDevice 

pub struct CountingDevice { /* private fields */ }

Wraps a device and counts the reads passing through it.

The counters are atomic and the type is Sync, so a driver reading from several threads is measured correctly rather than approximately.

Implementations

impl CountingDevice

pub fn new(inner: Arc<dyn BlockRead>) -> Self

Wrap inner, counting from zero.

pub fn reads(&self) -> u64

How many times the driver called read_at.

pub fn bytes(&self) -> u64

How many bytes those calls asked for, including the buffers of reads the device refused.

This is the request, not the transfer. See the module header for why bytes-moved is not reachable through BlockRead and why counting the request is what makes two drivers comparable.

pub fn reset(&self)

Start counting again from zero.

A mount reads a superblock and headers before the work being measured begins, and counting that in makes a small operation look like a large one. Reset after mounting, measure the operation, read the counters.

Trait Implementations

impl BlockRead for CountingDevice

fn read_at(&self, offset: u64, buf: &mut [u8]) -> Result<()>

Read exactly buf.len() bytes starting at offset (bytes from the start of the device).

fn size_bytes(&self) -> u64

Total device size in bytes. Used for bounds checks.