vtcode_commons/
memory.rs

1#![cfg_attr(
2    any(target_os = "macos", target_os = "linux"),
3    expect(
4        clippy::cast_possible_truncation,
5        reason = "RSS sampling casts platform ABI integer sizes to f64 for MB-scale reporting; truncation is acceptable."
6    )
7)]
8
9//! Resident Set Size (RSS) sampling for memory diagnostics.
10//!
11//! Used by the allocator benchmark (`vtcode bench-allocator`) to measure whether
12//! the global allocator returns memory to the OS after bursty/sparse workloads.
13//! Unlike `performance_profiler::get_memory_usage_mb` (Linux `/proc` only, fake
14//! fallback on macOS), this returns a real value on every supported platform.
15use std::time::Duration;
16
17/// Returns the current process Resident Set Size in **megabytes**, or `None` if
18/// it cannot be determined on the current platform.
19#[cfg(target_os = "macos")]
20#[allow(
21    deprecated,
22    unsafe_code,
23    unused_qualifications,
24    reason = "Intentional compatibility, platform, or test-only suppression."
25)] // libc::mach_task_self is deprecated; qualification is required here
26fn resident_set_size_mb() -> Option<f64> {
27    // SAFETY: `mach_task_basic_info` is a plain old data struct; zeroing it
28    // produces a valid (all-zero) starting value before `task_info` fills it.
29    let mut info: libc::mach_task_basic_info = unsafe { std::mem::zeroed() };
30    let mut count = (std::mem::size_of::<libc::mach_task_basic_info>() / std::mem::size_of::<libc::integer_t>())
31        as libc::mach_msg_type_number_t;
32    // SAFETY: `mach_task_self()` returns a send-right to the current task with
33    // no preconditions; it cannot fail to produce a valid port name.
34    let task = unsafe { libc::mach_task_self() };
35    // SAFETY: `task` is our own task port; `info` and `count` are valid
36    // out-pointers of the expected size, and `task_info` only writes them on
37    // success.
38    let ret = unsafe {
39        libc::task_info(task, libc::MACH_TASK_BASIC_INFO, &mut info as *mut _ as *mut libc::integer_t, &mut count)
40    };
41    if ret != libc::KERN_SUCCESS {
42        return None;
43    }
44    Some(info.resident_size as f64 / (1024.0 * 1024.0))
45}
46
47/// Returns the current process Resident Set Size in **megabytes**, or `None` if
48/// it cannot be determined on the current platform.
49#[cfg(target_os = "linux")]
50#[allow(
51    unsafe_code,
52    reason = "Intentional compatibility, platform, or test-only suppression."
53)]
54pub fn resident_set_size_mb() -> Option<f64> {
55    let contents = std::fs::read_to_string("/proc/self/statm").ok()?;
56    let field = contents.split_whitespace().nth(1)?;
57    let pages: f64 = field.parse().ok()?;
58    // SAFETY: `_SC_PAGESIZE` is a compile-time constant selector passed by value.
59    // `sysconf` only reads the selector and returns a `c_long`; it performs no
60    // mutable aliasing against process memory and has no preconditions on this
61    // input. The result is a stable system constant for the process lifetime.
62    let page_size = unsafe { libc::sysconf(libc::_SC_PAGESIZE) } as f64;
63    Some(pages * page_size / (1024.0 * 1024.0))
64}
65
66/// Fallback for unsupported platforms.
67#[cfg(not(any(target_os = "macos", target_os = "linux")))]
68pub fn resident_set_size_mb() -> Option<f64> {
69    None
70}
71
72/// Sample RSS once and return the value in MB (0.0 if unavailable).
73pub fn sample_rss_mb() -> f64 {
74    resident_set_size_mb().unwrap_or(0.0)
75}
76
77/// Sample RSS repeatedly, returning the maximum observed value in MB.
78/// Useful for capturing peak memory during a burst of activity.
79pub fn sample_peak_rss_mb(duration: Duration, poll_interval: Duration) -> f64 {
80    let start = std::time::Instant::now();
81    let mut peak = 0.0;
82    while start.elapsed() < duration {
83        let v = sample_rss_mb();
84        if v > peak {
85            peak = v;
86        }
87        std::thread::sleep(poll_interval);
88    }
89    peak
90}
vtcode_commons/memory.rs

vtcode_commons/
memory.rs
