Messages in this thread | | | Date | Tue, 21 Sep 2021 11:03:23 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup |
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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
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