From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Ingo Molnar <mingo@kernel.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup
Date: Tue, 21 Sep 2021 11:03:23 +0100 [thread overview]
Message-ID: <20210921100323.GL3959@techsingularity.net> (raw)
In-Reply-To: <YUmV/7puqVrYPfyL@hirez.programming.kicks-ass.net>
On Tue, Sep 21, 2021 at 10:21:19AM +0200, Peter Zijlstra wrote:
> On Tue, Sep 21, 2021 at 08:53:09AM +0100, Mel Gorman wrote:
> > On Tue, Sep 21, 2021 at 09:21:16AM +0200, Vincent Guittot wrote:
> > > On Mon, 20 Sept 2021 at 16:26, Mel Gorman <mgorman@techsingularity.net> wrote:
> > > >
> > > > The rq for curr is read during the function preamble, remove the
> > > > redundant lookup.
> > > >
> > > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> > > > ---
> > > > kernel/sched/fair.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > > > index ff69f245b939..038edfaaae9e 100644
> > > > --- a/kernel/sched/fair.c
> > > > +++ b/kernel/sched/fair.c
> > > > @@ -7190,7 +7190,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
> > > > if (cse_is_idle != pse_is_idle)
> > > > return;
> > > >
> > > > - update_curr(cfs_rq_of(se));
> > > > + update_curr(cfs_rq);
> > >
> > > se can have been modified by find_matching_se(&se, &pse)
> > >
> >
> > I still expected the cfs_rq to be the same, particularly given that the
> > context is about preempting the current task on a runqueue. Is that
> > wrong?
>
> Yes. There's a cfs_rq for every se. What we do in find_matching_se() is
> walk up the hiarachy until both are in the same cfs_rq, otherwse we
> cannot compare them.
>
> Fundamentally this means the effective cfs_rq also changes.
Ok, thanks. I'll read into this more but the patch is dead.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-09-21 10:03 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 14:26 [PATCH 0/2] Scale wakeup granularity relative to nr_running Mel Gorman
2021-09-20 14:26 ` [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup Mel Gorman
2021-09-21 7:21 ` Vincent Guittot
2021-09-21 7:53 ` Mel Gorman
2021-09-21 8:12 ` Vincent Guittot
2021-09-21 8:21 ` Peter Zijlstra
2021-09-21 10:03 ` Mel Gorman [this message]
2021-09-20 14:26 ` [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running Mel Gorman
2021-09-21 3:52 ` Mike Galbraith
2021-09-21 5:50 ` Mike Galbraith
2021-09-21 7:04 ` Mike Galbraith
2021-09-21 10:36 ` Mel Gorman
2021-09-21 12:32 ` Mike Galbraith
2021-09-21 14:03 ` Mel Gorman
2021-10-05 9:24 ` Peter Zijlstra
2021-09-22 5:22 ` Mike Galbraith
2021-09-22 13:20 ` Mel Gorman
2021-09-22 14:04 ` Mike Galbraith
2021-09-22 14:15 ` Vincent Guittot
2021-09-22 15:04 ` Mel Gorman
2021-09-22 16:00 ` Vincent Guittot
2021-09-22 17:38 ` Mel Gorman
2021-09-22 18:22 ` Vincent Guittot
2021-09-22 18:57 ` Mel Gorman
2021-09-23 1:47 ` Mike Galbraith
2021-09-23 8:40 ` Vincent Guittot
2021-09-23 9:21 ` Mike Galbraith
2021-09-23 12:41 ` Vincent Guittot
2021-09-23 13:14 ` Mike Galbraith
2021-09-27 11:17 ` Mel Gorman
2021-09-27 14:17 ` Mike Galbraith
2021-10-04 8:05 ` Mel Gorman
2021-10-04 16:37 ` Vincent Guittot
2021-10-05 7:41 ` Mel Gorman
2021-09-27 14:19 ` Vincent Guittot
2021-09-27 15:02 ` Mel Gorman
2021-09-23 12:24 ` Phil Auld
2021-10-05 10:36 ` Peter Zijlstra
2021-10-05 14:12 ` Phil Auld
2021-10-05 14:32 ` Peter Zijlstra
2021-10-05 10:28 ` Peter Zijlstra
2021-10-05 10:23 ` Peter Zijlstra
2021-10-05 9:41 ` Peter Zijlstra
2021-09-22 15:05 ` Vincent Guittot
2021-10-05 9:32 ` Peter Zijlstra
2021-10-03 3:07 ` wakeup_affine_weight() is b0rked - was " Mike Galbraith
2021-10-03 7:34 ` Barry Song
2021-10-03 14:52 ` Mike Galbraith
2021-10-03 21:06 ` Barry Song
2021-10-04 1:49 ` Mike Galbraith
2021-10-04 4:34 ` Mike Galbraith
2021-10-04 9:06 ` Mike Galbraith
2021-10-05 7:47 ` Mel Gorman
2021-10-05 8:42 ` Mike Galbraith
2021-10-05 9:31 ` Mel Gorman
2021-10-06 6:46 ` Mike Galbraith
2021-10-08 5:06 ` Mike Galbraith
2021-09-21 8:03 ` Vincent Guittot
2021-09-21 10:45 ` Mel Gorman
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