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scx_rusty: Simplify LoadBalancer::populate_tasks_by_load()

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Simplify LoadBalancer::populate_tasks_by_load() by cutting out the
heap allocation bits, by moving mutable accesses in front of immutable
ones. Because multiple immutable accesses (between bss and rodata) do
not conflict, we don't need the intermediate PID storage.

Signed-off-by: Daniel Müller <deso@posteo.net>
This commit is contained in:
Daniel Müller 2024-07-23 13:59:26 -07:00
parent 9a74f7b27f
commit 98af514972
1 changed files with 9 additions and 17 deletions
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26
scheds/rust/scx_rusty/src/load_balance.rs
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@ -678,35 +678,27 @@ impl<'a, 'b> LoadBalancer<'a, 'b> {
}
dom.queried_tasks = true;
// Read active_pids and update write_idx and gen.
//
// XXX - We can't read task_ctx inline because self.skel.bss()
// borrows mutably and thus conflicts with self.skel.maps().
// Read active_pids and update read_idx and gen.
const MAX_PIDS: u64 = bpf_intf::consts_MAX_DOM_ACTIVE_PIDS as u64;
let active_pids = &mut self.skel.bss_mut().dom_active_pids[dom.id];
let mut pids = vec![];
let (mut ridx, widx) = (active_pids.read_idx, active_pids.write_idx);
active_pids.read_idx = active_pids.write_idx;
active_pids.gen += 1;
let active_pids = &self.skel.bss().dom_active_pids[dom.id];
if widx - ridx > MAX_PIDS {
ridx = widx - MAX_PIDS;
}
for idx in ridx..widx {
let pid = active_pids.pids[(idx % MAX_PIDS) as usize];
pids.push(pid);
}
active_pids.read_idx = active_pids.write_idx;
active_pids.gen += 1;
// Read task_ctx and load.
let load_half_life = self.skel.rodata().load_half_life;
let maps = self.skel.maps();
let task_data = maps.task_data();
let now_mono = now_monotonic();
for pid in pids.iter() {
let key = unsafe { std::mem::transmute::<i32, [u8; 4]>(*pid) };
for idx in ridx..widx {
let pid = active_pids.pids[(idx % MAX_PIDS) as usize];
let key = unsafe { std::mem::transmute::<i32, [u8; 4]>(pid) };
if let Some(task_data_elem) = task_data.lookup(&key, libbpf_rs::MapFlags::ANY)? {
let task_ctx =
@ -733,7 +725,7 @@ impl<'a, 'b> LoadBalancer<'a, 'b> {
dom.tasks.insert(
TaskInfo {
pid: *pid,
pid,
load: OrderedFloat(load),
dom_mask: task_ctx.dom_mask,
preferred_dom_mask: task_ctx.preferred_dom_mask,