From: Tao Zhou <tao.zhou@linux.dev>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Mike Galbraith <efault@gmx.de>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Tao Zhou <tao.zhou@linux.dev>
Subject: Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers
Date: Fri, 29 Oct 2021 00:19:48 +0800 [thread overview]
Message-ID: <YXrNfHcfhp2LutiL@geo.homenetwork> (raw)
In-Reply-To: <20211028094834.1312-2-mgorman@techsingularity.net>
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
next prev parent reply other threads:[~2021-10-28 16:19 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 9:48 [PATCH v4 0/2] Reduce stacking and overscheduling Mel Gorman
2021-10-28 9:48 ` [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers Mel Gorman
2021-10-28 16:19 ` Tao Zhou [this message]
2021-10-29 8:42 ` Mel Gorman
2021-11-10 9:53 ` Tao Zhou
2021-11-10 15:40 ` Mike Galbraith
2021-10-29 15:17 ` Vincent Guittot
2021-10-30 3:11 ` Mike Galbraith
2021-10-30 4:12 ` Mike Galbraith
2021-11-01 8:56 ` Mel Gorman
2021-10-28 9:48 ` [PATCH 2/2] sched/fair: Increase wakeup_gran if current task has not executed the minimum granularity Mel Gorman
2021-10-29 16:07 ` Vincent Guittot
-- strict thread matches above, loose matches on Subject: below --
2021-10-21 14:56 [PATCH 0/2] Reduce stacking and overscheduling Mel Gorman
2021-10-21 14:56 ` [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers Mel Gorman
2021-10-22 10:26 ` Mike Galbraith
2021-10-22 11:05 ` Mel Gorman
2021-10-22 12:00 ` Mike Galbraith
2021-10-25 6:35 ` Mike Galbraith
2021-10-26 8:18 ` Mel Gorman
2021-10-26 10:15 ` Mike Galbraith
2021-10-26 10:41 ` Mike Galbraith
2021-10-26 11:57 ` Mel Gorman
2021-10-26 12:13 ` Mike Galbraith
2021-10-27 2:09 ` Mike Galbraith
2021-10-27 9:00 ` Mel Gorman
2021-10-27 10:18 ` Mike Galbraith
2021-11-09 11:56 ` Peter Zijlstra
2021-11-09 12:55 ` Mike Galbraith
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