Messages in this thread | | | Date | Fri, 29 Oct 2021 00:19:48 +0800 | From | Tao Zhou <> | Subject | Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers |
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Hi Mel,
On Thu, Oct 28, 2021 at 10:48:33AM +0100, Mel Gorman wrote:
> @@ -5865,6 +5865,14 @@ static void record_wakee(struct task_struct *p) > } > > if (current->last_wakee != p) { > + int min = __this_cpu_read(sd_llc_size) << 1; > + /* > + * Couple the wakee flips to the waker for the case where it > + * doesn't accrue flips, taking care to not push the wakee > + * high enough that the wake_wide() heuristic fails. > + */ > + if (current->wakee_flips > p->wakee_flips * min) > + p->wakee_flips++; > current->last_wakee = p; > current->wakee_flips++; > } > @@ -5895,7 +5903,7 @@ static int wake_wide(struct task_struct *p) > > if (master < slave) > swap(master, slave); > - if (slave < factor || master < slave * factor) > + if ((slave < factor && master < (factor>>1)*factor) || master < slave * factor)
So, the check like this include the above range:
if ((slave < factor && master < slave * factor) || master < slave * factor)
That "factor>>1" filter some.
If "slave < factor" is true and "master < (factor>>1)*factor" is false, then we check "master < slave * factor".(This is one path added by the check "&& master < (factor>>1)*factor"). In the latter check "slave < factor" must be true, the result of this check depend on slave in the range [factor, factor>>1] if there is possibility that "master < slave * factor". If slave in [factor>>1, 0], the check of "master < slave * factor" is absolutly false and this can be filtered if we use a variable to load the result of master < (factor>>1)*factor.
My random random inputs and continue confusing to move on.
Thanks, Tao
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