Lionel DARNIS
77262dd0af
malloc_trim(0) was called at the end of every update() and view(), reaching 60-200 Hz during typical scrolling, resize, or animation. Each call walks the glibc heap (10 us to several ms depending on fragmentation) and could consume a substantial fraction of the frame budget in worst cases. Throttle trim() to once per second using a thread-local Instant, preserving the existing API. RSS stays bounded (1 Hz is enough to release collectable pages soon after) while per-frame cost becomes a single thread-local check plus a duration comparison. No call-site changes required; the three existing trim(0) invocations in src/app/cosmic.rs (update, view multi-window, view single-window) now fall under the throttle transparently.
55 lines
1.7 KiB
Rust
55 lines
1.7 KiB
Rust
// Copyright 2025 System76 <info@system76.com>
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// SPDX-License-Identifier: MPL-2.0
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use std::cell::Cell;
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use std::os::raw::c_int;
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use std::time::{Duration, Instant};
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const M_MMAP_THRESHOLD: c_int = -3;
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/// Minimum interval between two actual `malloc_trim` calls.
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///
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/// `trim` is called at the end of every `update()` and `view()`, which can
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/// reach 60-200 Hz during typical scrolling, resize, or animation. Each
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/// `malloc_trim` walks the glibc heap (10 µs to several ms depending on
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/// fragmentation), so calling it at render frequency can consume a
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/// substantial fraction of the frame budget. Throttling to 1 Hz keeps RSS
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/// bounded while removing the per-frame syscall from the hot path.
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const TRIM_MIN_INTERVAL: Duration = Duration::from_millis(1000);
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thread_local! {
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static LAST_TRIM: Cell<Option<Instant>> = const { Cell::new(None) };
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}
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unsafe extern "C" {
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fn malloc_trim(pad: usize);
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fn mallopt(param: c_int, value: c_int) -> c_int;
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}
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/// Throttled wrapper over `malloc_trim`. Safe to call at render frequency:
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/// consecutive calls within `TRIM_MIN_INTERVAL` (per-thread) skip the syscall.
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#[inline]
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pub fn trim(pad: usize) {
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LAST_TRIM.with(|last| {
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let now = Instant::now();
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let should_trim = match last.get() {
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None => true,
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Some(prev) => now.duration_since(prev) >= TRIM_MIN_INTERVAL,
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};
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if should_trim {
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last.set(Some(now));
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unsafe {
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malloc_trim(pad);
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}
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}
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});
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}
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/// Prevents glibc from hoarding memory via memory fragmentation.
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#[inline]
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pub fn limit_mmap_threshold(threshold: i32) {
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unsafe {
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mallopt(M_MMAP_THRESHOLD, threshold as c_int);
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}
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}
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