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scx_p2dq: Fix stalls in affinitized tasks #2014

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Merged
merged 1 commit into from
May 28, 2025
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scx_p2dq: Fix stalls in affinitized tasks #2014

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31 changes: 21 additions & 10 deletions scheds/rust/scx_p2dq/src/bpf/main.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -534,6 +534,10 @@ static s32 pick_idle_affinitized_cpu(struct task_struct *p, task_ctx *taskc,
}
}

if (llcx->cpumask)
bpf_cpumask_and(mask, cast_mask(llcx->cpumask),
p->cpus_ptr);

// Next try to find an idle CPU in the LLC
cpu = scx_bpf_pick_idle_cpu(cast_mask(mask), 0);
if (cpu >= 0) {
Expand Down Expand Up @@ -797,10 +801,13 @@ static __always_inline void async_p2dq_enqueue(struct enqueue_promise *ret,
* Per-cpu kthreads are considered interactive and dispatched directly
* into the local DSQ.
*/
if ((p->flags & PF_KTHREAD) && p->cpus_ptr == &p->cpus_mask && p->nr_cpus_allowed != nr_cpus &&
if ((p->flags & PF_KTHREAD) &&
p->cpus_ptr == &p->cpus_mask &&
p->nr_cpus_allowed != nr_cpus &&
bpf_cpumask_test_cpu(cpu, p->cpus_ptr) &&
kthreads_local) {
stat_inc(P2DQ_STAT_DIRECT);
scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL, dsq_time_slices[0], enq_flags);
scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL_ON|cpu, dsq_time_slices[0], enq_flags);
ret->kind = P2DQ_ENQUEUE_PROMISE_COMPLETE;
return;
}
Expand All @@ -812,15 +819,19 @@ static __always_inline void async_p2dq_enqueue(struct enqueue_promise *ret,
}

// Handle affinitized tasks separately
if (!taskc->all_cpus) {
if (!taskc->all_cpus ||
(p->cpus_ptr == &p->cpus_mask &&
p->nr_cpus_allowed != nr_cpus)) {
bool is_idle = false;
cpu = pick_idle_affinitized_cpu(p, taskc, cpu, &is_idle);
if (!(cpuc = lookup_cpu_ctx(cpu)) ||
!(llcx = lookup_llc_ctx(cpuc->llc_id))) {
scx_bpf_error("invalid lookup");
ret->kind = P2DQ_ENQUEUE_PROMISE_COMPLETE;
return;
}
if (!bpf_cpumask_test_cpu(cpu, p->cpus_ptr))
cpu = pick_idle_affinitized_cpu(p, taskc, cpu, &is_idle);

// if (!(cpuc = lookup_cpu_ctx(cpu)) ||
// !(llcx = lookup_llc_ctx(cpuc->llc_id))) {
// scx_bpf_error("invalid lookup");
// ret->kind = P2DQ_ENQUEUE_PROMISE_COMPLETE;
// return;
// }

scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL_ON|cpu, taskc->slice_ns, enq_flags);
if (is_idle) {
Expand Down