From: Mel Gorman <mgorman@techsingularity.net>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>,
Peter Zijlstra <peterz@infradead.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 2/2] sched/fair: Scale wakeup granularity relative to nr_running
Date: Mon, 27 Sep 2021 12:17:30 +0100 [thread overview]
Message-ID: <20210927111730.GG3959@techsingularity.net> (raw)
In-Reply-To: <CAKfTPtDHYtskM7wR0w=fDry+6JJae2_q8Lw7ETcW_gBJ+n4NBA@mail.gmail.com>
On Thu, Sep 23, 2021 at 02:41:06PM +0200, Vincent Guittot wrote:
> On Thu, 23 Sept 2021 at 11:22, Mike Galbraith <efault@gmx.de> wrote:
> >
> > On Thu, 2021-09-23 at 10:40 +0200, Vincent Guittot wrote:
> > >
> > > a 100us value should even be enough to fix Mel's problem without
> > > impacting common wakeup preemption cases.
> >
> > It'd be nice if it turn out to be something that simple, but color me
> > skeptical. I've tried various preemption throttling schemes, and while
>
> Let's see what the results will show. I tend to agree that this will
> not be enough to cover all use cases and I don't see any other way to
> cover all cases than getting some inputs from the threads about their
> latency fairness which bring us back to some kind of latency niceness
> value
>
Unfortunately, I didn't get a complete set of results but enough to work
with. The missing tests have been requeued. The figures below are based
on a single-socket Skylake machine with 8 CPUs as it had the most set of
results and is the basic case.
The reported kernels are
vanilla: vanilla 5.15-rc1
sched-scalewakegran-v2r4: My patch
sched-moveforward-v1r1: Vincent's patch
hackbench-process-pipes
5.15.0-rc1 5.15.0-rc1 5.15.0-rc1
vanilla sched-scalewakegran-v2r4 sched-moveforward-v1r1
Amean 1 0.3253 ( 0.00%) 0.3330 ( -2.36%) 0.3257 ( -0.10%)
Amean 4 0.8300 ( 0.00%) 0.7570 ( 8.80%) 0.7560 ( 8.92%)
Amean 7 1.1003 ( 0.00%) 1.1457 * -4.12%* 1.1163 ( -1.45%)
Amean 12 1.7263 ( 0.00%) 1.6393 * 5.04%* 1.5963 * 7.53%*
Amean 21 3.0063 ( 0.00%) 2.6590 * 11.55%* 2.4487 * 18.55%*
Amean 30 4.2323 ( 0.00%) 3.5657 * 15.75%* 3.3410 * 21.06%*
Amean 48 6.5657 ( 0.00%) 5.4180 * 17.48%* 5.0857 * 22.54%*
Amean 79 10.4867 ( 0.00%) 8.4357 * 19.56%* 7.9563 * 24.13%*
Amean 110 14.8880 ( 0.00%) 11.0423 * 25.83%* 10.7407 * 27.86%*
Amean 141 19.2083 ( 0.00%) 14.0820 * 26.69%* 13.3780 * 30.35%*
Amean 172 23.4847 ( 0.00%) 16.9880 * 27.66%* 16.4293 * 30.04%*
Amean 203 27.3763 ( 0.00%) 20.2480 * 26.04%* 19.6430 * 28.25%*
Amean 234 31.3707 ( 0.00%) 23.2477 * 25.89%* 22.8287 * 27.23%*
Amean 265 35.4663 ( 0.00%) 26.2483 * 25.99%* 25.8683 * 27.06%*
Amean 296 39.2380 ( 0.00%) 29.4237 * 25.01%* 28.8727 * 26.42%*
For hackbench, either Vincent or my patch has a similar impact.
tbench4
5.15.0-rc1 5.15.0-rc1 5.15.0-rc1
vanillasched-scalewakegran-v2r4 sched-moveforward-v1r1
Hmean 1 598.71 ( 0.00%) 608.31 * 1.60%* 586.05 * -2.11%*
Hmean 2 1096.74 ( 0.00%) 1110.07 * 1.22%* 1106.70 * 0.91%*
Hmean 4 1529.35 ( 0.00%) 1531.20 * 0.12%* 1551.11 * 1.42%*
Hmean 8 2824.32 ( 0.00%) 2847.96 * 0.84%* 2684.21 * -4.96%*
Hmean 16 2573.30 ( 0.00%) 2591.77 * 0.72%* 2445.41 * -4.97%*
Hmean 32 2518.77 ( 0.00%) 2532.70 * 0.55%* 2409.30 * -4.35%*
For tbench, it's ok for lower thread counts for 8 threads (machine
overloaded), Vincent's patch regresses slightly. With these test runs,
I don't have detailed information as to why but the most likely solution
is that preemption gets disabled prematurely.
specjbb
5.15.0-rc1 5.15.0-rc1 5.15.0-rc1
vanillasched-scalewakegran-v2r4 sched-moveforward-v1r1
Hmean tput-1 71199.00 ( 0.00%) 69492.00 * -2.40%* 71126.00 * -0.10%*
Hmean tput-2 154478.00 ( 0.00%) 146060.00 * -5.45%* 153073.00 * -0.91%*
Hmean tput-3 211889.00 ( 0.00%) 209386.00 * -1.18%* 219434.00 * 3.56%*
Hmean tput-4 257842.00 ( 0.00%) 248012.00 * -3.81%* 262903.00 * 1.96%*
Hmean tput-5 253506.00 ( 0.00%) 242511.00 * -4.34%* 250828.00 * -1.06%*
Hmean tput-6 246202.00 ( 0.00%) 236480.00 * -3.95%* 244236.00 * -0.80%*
Hmean tput-7 241133.00 ( 0.00%) 230905.00 * -4.24%* 237619.00 * -1.46%*
Hmean tput-8 237983.00 ( 0.00%) 230010.00 * -3.35%* 235275.00 * -1.14%*
For specjbb, it's different again, Vincent's patch is better for the
overloaded case but both patches show light regressions.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2021-09-27 11:17 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
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 [this message]
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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