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simplify the swap search algorithm

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turns out that prioritizing pages beyond LRU does not improve
performance at all -- really hurts performance.

Also making the OOM target a bit smaller so that the system
feels a bit more responsive between OOM events.
This commit is contained in:
bunnie 2024-05-28 21:25:21 +08:00
parent 1f72c8cd38
commit 8a58db8936
1 changed files with 2 additions and 18 deletions
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20
services/xous-swapper/src/main.rs
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@ -51,7 +51,7 @@
mod debug;
mod platform;
use core::fmt::Write;
use std::collections::{BinaryHeap, VecDeque};
use std::collections::BinaryHeap;
use std::fmt::Debug;
use std::thread;
use std::thread::sleep;
@ -67,7 +67,7 @@ use xous::{MemoryFlags, MemoryRange, Message, Result, CID, PID, SID};
/// are imprecise, in that there is a chance that one target is active during another
/// invocation of a routine. This is because the hard OOM handler is entirely asynchronous
/// and could be invoked at any time, including while we are trying to handle a soft OOM.
const HARD_OOM_PAGE_TARGET: usize = 32;
const HARD_OOM_PAGE_TARGET: usize = 24;
/// Target of pages to free in case of OOM Doom
#[cfg(feature = "oom-doom")]
const OOM_DOOM_PAGE_TARGET: usize = 48;
@ -76,11 +76,6 @@ const OOM_DOOM_PAGE_TARGET: usize = 48;
#[cfg(feature = "oom-doom")]
const OOM_DOOM_POLL_INTERVAL_MS: u64 = 1057;
/// Virtual address prefixes to de-prioritize in the OomDoom sweep
/// 0 - text region
/// 4 - message region
const KEEP_VADDR_PREFIXES: [u8; 2] = [0u8, 4u8];
/// userspace swapper -> kernel ABI
/// This ABI is copy-paste synchronized with what's in the kernel. It's left out of
/// xous-rs so that we can change it without having to push crates to crates.io.
@ -606,10 +601,6 @@ fn swap_handler(
let mut errs: usize = 0;
let mut wired: usize = 0;
// A holding variable for items that we're de-prioritizing from removal. We only try these
// if we've exhausted all the other options.
let mut deprioritized = VecDeque::new();
while pages_to_free > 0 {
if let Some(candidate) = alloc_heap.pop() {
if candidate.is_wired()
@ -619,16 +610,9 @@ fn swap_handler(
{
wired += 1;
} else {
if KEEP_VADDR_PREFIXES.iter().find(|&&x| x == candidate.vaddr_prefix()).is_some() {
log::trace!("De-prioritizing {:x?}", candidate);
deprioritized.push_back(candidate);
continue;
}
// error is ignored because the correct behavior on error is to try another page
write_to_swap_inner(ss, candidate, &mut errs, &mut pages_to_free).ok();
}
} else if let Some(candidate) = deprioritized.pop_front() {
write_to_swap_inner(ss, candidate, &mut errs, &mut pages_to_free).ok();
} else {
writeln!(
DebugUart {},