From: Vincent Guittot <vincent.guittot@linaro.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Ingo Molnar <mingo@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Phil Auld <pauld@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Quentin Perret <quentin.perret@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <Morten.Rasmussen@arm.com>,
Hillf Danton <hdanton@sina.com>, Parth Shah <parth@linux.ibm.com>,
Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH v4 00/10] sched/fair: rework the CFS load balance
Date: Wed, 30 Oct 2019 17:35:53 +0100 [thread overview]
Message-ID: <CAKfTPtBVWenCt5qLvow6ubB6a8c1gdPfW8-fWaKAa0k8b47m9Q@mail.gmail.com> (raw)
In-Reply-To: <20191030162440.GO3016@techsingularity.net>
On Wed, 30 Oct 2019 at 17:24, Mel Gorman <mgorman@techsingularity.net> wrote:
>
> On Mon, Oct 21, 2019 at 09:50:38AM +0200, Ingo Molnar wrote:
> > > <SNIP>
> >
> > Thanks, that's an excellent series!
> >
>
> Agreed despite the level of whining and complaining I made during the
> review.
Thanks for the review.
I haven't gone through all your comments yet but will do in the coming days
>
> > I've queued it up in sched/core with a handful of readability edits to
> > comments and changelogs.
> >
> > There are some upstreaming caveats though, I expect this series to be a
> > performance regression magnet:
> >
> > - load_balance() and wake-up changes invariably are such: some workloads
> > only work/scale well by accident, and if we touch the logic it might
> > flip over into a less advantageous scheduling pattern.
> >
> > - In particular the changes from balancing and waking on runnable load
> > to full load that includes blocking *will* shift IO-intensive
> > workloads that you tests don't fully capture I believe. You also made
> > idle balancing more aggressive in essence - which might reduce cache
> > locality for some workloads.
> >
> > A full run on Mel Gorman's magic scalability test-suite would be super
> > useful ...
> >
>
> I queued this back on the 21st and it took this long for me to get back
> to it.
>
> What I tested did not include the fix for the last patch so I cannot say
> the data is that useful. I also failed to include something that exercised
> the IO paths in a way that idles rapidly as that can catch interesting
> details (usually cpufreq related but sometimes load-balancing related).
> There was no real thinking behind this decision, I just used an old
> collection of tests to get a general feel for the series.
>
> Most of the results were performance-neutral and some notable gains
> (kernel compiles were 1-6% faster depending on the -j count). Hackbench
> saw a disproportionate gain in terms of performance but I tend to be wary
> of hackbench as improving it is rarely a universal win.
> There tends to be some jitter around the point where a NUMA nodes worth
> of CPUs gets overloaded. tbench (mmtests configuation network-tbench) on
> a NUMA machine showed gains for low thread counts and high thread counts
> but a loss near the boundary where a single node would get overloaded.
>
> Some NAS-related workloads saw a drop in performance on NUMA machines
> but the size class might be too small to be certain, I'd have to rerun
> with the D class to be sure. The biggest strange drop in performance
> was the elapsed time to run the git test suite (mmtests configuration
> workload-shellscripts modified to use a fresh XFS partition) took 17.61%
> longer to execute on a UMA Skylake machine. This *might* be due to the
> missing fix because it is mostly a single-task workload.
>
> I'm not going to go through the results in detail because I think another
> full round of testing would be required to take the fix into account. I'd
> also prefer to wait to see if the review results in any material change
> to the series.
>
> --
> Mel Gorman
> SUSE Labs
next prev parent reply other threads:[~2019-10-30 16:36 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 13:26 [PATCH v4 00/10] sched/fair: rework the CFS load balance Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 01/11] sched/fair: clean up asym packing Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Clean " tip-bot2 for Vincent Guittot
2019-10-30 14:51 ` [PATCH v4 01/11] sched/fair: clean " Mel Gorman
2019-10-30 16:03 ` Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 02/11] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Rename sg_lb_stats::sum_nr_running " tip-bot2 for Vincent Guittot
2019-10-30 14:53 ` [PATCH v4 02/11] sched/fair: rename sum_nr_running " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 03/11] sched/fair: remove meaningless imbalance calculation Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Remove " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 04/11] sched/fair: rework load_balance Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Rework load_balance() tip-bot2 for Vincent Guittot
2019-10-30 15:45 ` [PATCH v4 04/11] sched/fair: rework load_balance Mel Gorman
2019-10-30 16:16 ` Valentin Schneider
2019-10-31 9:09 ` Vincent Guittot
2019-10-31 10:15 ` Mel Gorman
2019-10-31 11:13 ` Vincent Guittot
2019-10-31 11:40 ` Mel Gorman
2019-11-08 16:35 ` Vincent Guittot
2019-11-08 18:37 ` Mel Gorman
2019-11-12 10:58 ` Vincent Guittot
2019-11-12 15:06 ` Mel Gorman
2019-11-12 15:40 ` Vincent Guittot
2019-11-12 17:45 ` Mel Gorman
2019-11-18 13:50 ` Ingo Molnar
2019-11-18 13:57 ` Vincent Guittot
2019-11-18 14:51 ` Mel Gorman
2019-10-18 13:26 ` [PATCH v4 05/11] sched/fair: use rq->nr_running when balancing load Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-30 15:54 ` [PATCH v4 05/11] sched/fair: use " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 06/11] sched/fair: use load instead of runnable load in load_balance Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Use load instead of runnable load in load_balance() tip-bot2 for Vincent Guittot
2019-10-30 15:58 ` [PATCH v4 06/11] sched/fair: use load instead of runnable load in load_balance Mel Gorman
2019-10-18 13:26 ` [PATCH v4 07/11] sched/fair: evenly spread tasks when not overloaded Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Spread out tasks evenly " tip-bot2 for Vincent Guittot
2019-10-30 16:03 ` [PATCH v4 07/11] sched/fair: evenly spread tasks " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 08/11] sched/fair: use utilization to select misfit task Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 09/11] sched/fair: use load instead of runnable load in wakeup path Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 10/11] sched/fair: optimize find_idlest_group Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Optimize find_idlest_group() tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 11/11] sched/fair: rework find_idlest_group Vincent Guittot
2019-10-21 9:12 ` [tip: sched/core] sched/fair: Rework find_idlest_group() tip-bot2 for Vincent Guittot
2019-10-22 16:46 ` [PATCH] sched/fair: fix rework of find_idlest_group() Vincent Guittot
2019-10-23 7:50 ` Chen, Rong A
2019-10-30 16:07 ` Mel Gorman
2019-11-18 17:42 ` [tip: sched/core] sched/fair: Fix " tip-bot2 for Vincent Guittot
2019-11-22 14:37 ` [PATCH] sched/fair: fix " Valentin Schneider
2019-11-25 9:16 ` Vincent Guittot
2019-11-25 11:03 ` Valentin Schneider
2019-11-20 11:58 ` [PATCH v4 11/11] sched/fair: rework find_idlest_group Qais Yousef
2019-11-20 13:21 ` Vincent Guittot
2019-11-20 16:53 ` Vincent Guittot
2019-11-20 17:34 ` Qais Yousef
2019-11-20 17:43 ` Vincent Guittot
2019-11-20 18:10 ` Qais Yousef
2019-11-20 18:20 ` Vincent Guittot
2019-11-20 18:27 ` Qais Yousef
2019-11-20 19:28 ` Vincent Guittot
2019-11-20 19:55 ` Qais Yousef
2019-11-21 14:58 ` Qais Yousef
2019-11-22 14:34 ` Valentin Schneider
2019-11-25 9:59 ` Vincent Guittot
2019-11-25 11:13 ` Valentin Schneider
2019-10-21 7:50 ` [PATCH v4 00/10] sched/fair: rework the CFS load balance Ingo Molnar
2019-10-21 8:44 ` Vincent Guittot
2019-10-21 12:56 ` Phil Auld
2019-10-24 12:38 ` Phil Auld
2019-10-24 13:46 ` Phil Auld
2019-10-24 14:59 ` Vincent Guittot
2019-10-25 13:33 ` Phil Auld
2019-10-28 13:03 ` Vincent Guittot
2019-10-30 14:39 ` Phil Auld
2019-10-30 16:24 ` Dietmar Eggemann
2019-10-30 16:35 ` Valentin Schneider
2019-10-30 17:19 ` Phil Auld
2019-10-30 17:25 ` Valentin Schneider
2019-10-30 17:29 ` Phil Auld
2019-10-30 17:28 ` Vincent Guittot
2019-10-30 17:44 ` Phil Auld
2019-10-30 17:25 ` Vincent Guittot
2019-10-31 13:57 ` Phil Auld
2019-10-31 16:41 ` Vincent Guittot
2019-10-30 16:24 ` Mel Gorman
2019-10-30 16:35 ` Vincent Guittot [this message]
2019-11-18 13:15 ` Ingo Molnar
2019-11-25 12:48 ` Valentin Schneider
2020-01-03 16:39 ` Valentin Schneider
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