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minor refactor of scx_rusty #31

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Merged
merged 1 commit into from
Dec 14, 2023
Merged

minor refactor of scx_rusty #31

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18 changes: 7 additions & 11 deletions scheds/rust-user/scx_rusty/src/bpf/main.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -425,18 +425,21 @@ s32 BPF_STRUCT_OPS(rusty_select_cpu, struct task_struct *p, s32 prev_cpu,
if (!(taskc = lookup_task_ctx(p)) || !(p_cpumask = taskc->cpumask))
goto enoent;

if (kthreads_local &&
(p->flags & PF_KTHREAD) && p->nr_cpus_allowed == 1) {
if (p->nr_cpus_allowed == 1) {
cpu = prev_cpu;
stat_add(RUSTY_STAT_DIRECT_DISPATCH, 1);
if (kthreads_local && (p->flags & PF_KTHREAD)) {
stat_add(RUSTY_STAT_DIRECT_DISPATCH, 1);
} else {
stat_add(RUSTY_STAT_PINNED, 1);
}
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@Byte-Lab Byte-Lab Dec 14, 2023

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I think we can simplify the if on line 442 by removing the first p->nr_cpus_allowed > 1 clause, which should always be true now that we're always doing local dispatching if p->nr_cpus_allowed == 1

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@jordalgo jordalgo Dec 14, 2023

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Good call. Will fix.

goto direct;
}

/*
* If WAKE_SYNC and the machine isn't fully saturated, wake up @p to the
* local dsq of the waker.
*/
if (p->nr_cpus_allowed > 1 && (wake_flags & SCX_WAKE_SYNC)) {
if (wake_flags & SCX_WAKE_SYNC) {
struct task_struct *current = (void *)bpf_get_current_task();

if (!(BPF_CORE_READ(current, flags) & PF_EXITING) &&
Expand Down Expand Up @@ -475,13 +478,6 @@ s32 BPF_STRUCT_OPS(rusty_select_cpu, struct task_struct *p, s32 prev_cpu,
}
}

/* If only one CPU is allowed, dispatch */
if (p->nr_cpus_allowed == 1) {
stat_add(RUSTY_STAT_PINNED, 1);
cpu = prev_cpu;
goto direct;
}

has_idle_cores = !bpf_cpumask_empty(idle_smtmask);

/* did @p get pulled out to a foreign domain by e.g. greedy execution? */
Expand Down