Messages in this thread Patch in this message | | | Date | Mon, 9 Dec 2019 17:16:27 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] schied/fair: Skip updating "contrib" without load |
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On Sat, Dec 07, 2019 at 12:14:22AM +0800, Peng Wang wrote: > We only update load_sum/runnable_load_sum/util_sum with > decayed old sum when load is clear.
What you're saying is that because of the:
if (!load) runnable = running = 0;
clause in ___update_load_sum(), all the actual users of @contrib in accumulate_sum():
if (load) sa->load_sum += load * contrib; if (runnable) sa->runnable_load_sum += runnable * contrib; if (running) sa->util_sum += contrib << SCHED_CAPACITY_SHIFT;
don't happen, and therefore we don't care what @contrib actually is and calculating it is pointless.
I suppose that is so. did you happen to have performance numbers? Also, I'm thinking this wants a comment.
> Signed-off-by: Peng Wang <rocking@linux.alibaba.com> > --- > kernel/sched/pelt.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index a96db50..4392953 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -129,8 +129,9 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) > * Step 2 > */ > delta %= 1024; > - contrib = __accumulate_pelt_segments(periods, > - 1024 - sa->period_contrib, delta); > + if (load) > + contrib = __accumulate_pelt_segments(periods, > + 1024 - sa->period_contrib, delta); > } > sa->period_contrib = delta; > > -- > 1.8.3.1 >
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