Messages in this thread Patch in this message | | | Date | Fri, 15 Oct 2021 09:26:41 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] sched/fair: document the slow path and fast path in select_task_rq_fair |
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On Fri, 15 Oct 2021 12:14:12 +0800 Barry Song <21cnbao@gmail.com> wrote:
> --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6951,6 +6951,11 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) > break; > } > > + /* > + * This is usually true only for WF_EXEC and WF_FORK, for WF_TTWU > + * it is almost always false as sched_domain hasn't SD_BALANCE_WAKE > + * in default
Comments are fine, but the above needs some grammar work.
/* * Usually only true for WF_EXEC and WF_FORK, as * sched_domains usually do not have SD_BALANCE_WAKE set. */
?
> + */ > if (tmp->flags & sd_flag) > sd = tmp; > else if (!want_affine) > @@ -6958,7 +6963,11 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) > } > > if (unlikely(sd)) { > - /* Slow path */ > + /* > + * Slow path, usually only for WF_EXEC and WF_FORK; WF_TTWU almost > + * always goes to fast path as sched_domain hasn't SD_BALANCE_WAKE > + * in default > + */
As the only way to have sd set, is from the above if statement, I believe this comment is redundant.
-- Steve
> new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); > } else if (wake_flags & WF_TTWU) { /* XXX always ? */ > /* Fast path */
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