Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1222115
| From | Morten Rasmussen <morten.rasmussen@arm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig |
| Date | 2015-09-10 13:10 +0200 |
| Message-ID | <q77TQ-838-3@gated-at.bofh.it> (permalink) |
| References | (5 earlier) <q6qca-48n-43@gated-at.bofh.it> <q6qFd-4GE-21@gated-at.bofh.it> <q6s4j-6PU-29@gated-at.bofh.it> <q6ta2-8oh-17@gated-at.bofh.it> <q6W2m-7YC-19@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Wed, Sep 09, 2015 at 03:23:43PM -0700, bsegall@google.com wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > On Tue, Sep 08, 2015 at 03:31:58PM +0100, Morten Rasmussen wrote:
> >> On Tue, Sep 08, 2015 at 02:52:05PM +0200, Peter Zijlstra wrote:
> >> > > Tricky that, LOAD_AVG_MAX very much relies on the unit being 1<<10.
> >>
> >> I don't get why LOAD_AVG_MAX relies on the util_avg shifting being
> >> 1<<10, it is just the sum of the geometric series and the upper bound of
> >> util_sum?
> >
> > It needs a 1024, it might just have been the 1024 ns we use a period
> > instead of the scale unit though.
> >
> > The LOAD_AVG_MAX is the number where adding a next element to the series
> > doesn't change the result anymore, so scaling it up will allow more
> > significant elements to the series before we bottom out, which is the _N
> > thing.
> >
>
> Yes, as the comments say, the 1024ns unit is arbitrary (and is an
> average of not-quite-microseconds instead of just nanoseconds to allow
> more bits to load.weight when we multiply load.weight by this number).
> In fact there are two arbitrary 1024 units here, which are technically
> unrelated and are both unrelated to SCHED_LOAD_RESOLUTION/etc - we
> operate on units of almost-microseconds and we also do decays every
> almost-millisecond.
>
> There appears to be a bunch of confusion in the current code around
> util_sum/util_avg which appears to using SCHED_LOAD_SCALE
> for a fixed-point percentage or something, which is at least reasonable,
> but is initializing it as scale_load_down(SCHED_LOAD_SCALE), which
> results in either initializing as 100% or .1% depending on RESOLUTION.
> This'll get clobbered on first update, but if it needs to be
> initialized, it should either get initialized to something sane or at
> least consistent.
This is what I thought too. The whole geometric series math is completely
independent of the scale used for priority in load_avg and the fixed
point shifting used for util_avg.
> load_sum/load_avg appear to be scale_load_down()ed properly, and appear
> to be used as such at a quick glance.
I don't think shifting by SCHED_LOAD_SHIFT in __update_load_avg() is
right:
sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
util_avg is initialized to low resolution (>> SCHED_LOAD_RESOLUTION):
sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
so it appear to be intended to be using low resolution like load_avg
(weight is scaled down before it is passed into __update_load_avg()),
but util_avg is shifted up to high resolution. It should be:
sa->util_avg = (sa->util_sum << (SCHED_LOAD_SHIFT -
SCHED_LOAD_SHIFT)) / LOAD_AVG_MAX;
to be consistent.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-09-07 17:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-07 18:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-09-07 21:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-07 21:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-09-08 14:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 09:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-08 14:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-08 15:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 16:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-08 16:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 16:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-08 16:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-08 17:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-10 00:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-10 13:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-10 13:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-10 14:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-11 10:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-10 19:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-08 18:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-09 11:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-09 11:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-09 13:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-11 19:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-17 12:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-17 12:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-21 11:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-21 19:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-22 09:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Leo Yan <leo.yan@linaro.org> - 2015-09-11 09:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-11 12:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Leo Yan <leo.yan@linaro.org> - 2015-09-11 16:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-10 05:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-10 12:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 15:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-08 16:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 17:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-09-08 15:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Vincent Guittot <vincent.guittot@linaro.org> - 2015-09-08 16:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-09-08 16:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-10 06:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-10 12:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-11 10:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-11 12:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-11 19:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-12 04:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-14 19:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-14 15:00 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-14 19:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-15 08:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-15 19:20 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-16 04:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig bsegall@google.com - 2015-09-16 19:10 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Yuyang Du <yuyang.du@intel.com> - 2015-09-17 12:30 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Morten Rasmussen <morten.rasmussen@arm.com> - 2015-09-15 10:40 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-16 17:50 +0200
Re: [PATCH 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Peter Zijlstra <peterz@infradead.org> - 2015-09-08 13:50 +0200
[tip:sched/core] sched/fair: Get rid of scaling utilization by capacity_orig tip-bot for Dietmar Eggemann <tipbot@zytor.com> - 2015-09-13 13:10 +0200
csiph-web