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From: Chris Wilson <chris@chris-wilson.co.uk>
To: Andy Lutomirski <luto@kernel.org>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Abysmal scheduler performance in Linus' tree?
Date: Wed, 06 Sep 2017 10:15:33 +0100
Message-ID: <150468933360.28581.16446660443497682079@mail.alporthouse.com> (raw)
In-Reply-To: <CALCETrXZ9LZ+T5T-FS2hy0TU_c0MWPYokN9-d0qx3-1jFOOHcw@mail.gmail.com>

Quoting Andy Lutomirski (2017-09-06 06:13:39)
> I'm running e7d0c41ecc2e372a81741a30894f556afec24315 from Linus' tree
> today, and I'm seeing abysmal scheduler performance.  Running make -j4
> ends up with all the tasks on CPU 3 most of the time (on my
> 4-logical-thread laptop).  taskset -c 0 whatever puts whatever on CPU
> 0, but plain while true; do true; done puts the infinite loop on CPU 3
> right along with the make -j4 tasks.
> 
> This is on Fedora 26, and I don't think I'm doing anything weird.
> systemd has enabled the cpu controller, but it doesn't seem to have
> configured anything or created any non-root cgroups.
> 
> Just a heads up.  I haven't tried to diagnose it at all.

There is an issue on !llc machines arising from numa_wake_wide() where
processes are not spread widely across the low-power cores:
https://patchwork.kernel.org/patch/9875581/

The patch we are using to fix the regression is
https://cgit.freedesktop.org/drm-intel/commit/?h=topic/core-for-CI&id=6c362d9657293d700a8299acbeb2f1e24378f488
-Chris

  parent reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-06  5:13 Andy Lutomirski
2017-09-06  8:25 ` Peter Zijlstra
2017-09-06  8:59   ` Andy Lutomirski
2017-09-06  9:03     ` Peter Zijlstra
2017-09-06 16:14       ` Peter Zijlstra
2017-09-07  6:15         ` Mike Galbraith
2017-09-07  7:31           ` Ingo Molnar
2017-09-07  9:13           ` [PATCH] sched/cpuset/pm: Fix cpuset vs suspend-resume Peter Zijlstra
2017-09-07  9:26             ` Peter Zijlstra
2017-09-07 10:54               ` Rafael J. Wysocki
2017-09-07 20:38               ` Tejun Heo
2017-09-07 10:33             ` [tip:sched/urgent] sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs tip-bot for Peter Zijlstra
2017-09-06  9:15 ` Chris Wilson [this message]
2017-09-06  9:24   ` Abysmal scheduler performance in Linus' tree? Peter Zijlstra
     [not found]     ` <150469312649.28581.17626550155735691534@mail.alporthouse.com>
2017-09-06 10:44       ` Peter Zijlstra
2017-09-06 10:51         ` Peter Zijlstra
2017-09-07  8:16           ` [tip:sched/urgent] sched/fair: Fix wake_affine_llc() balancing rules tip-bot for Peter Zijlstra

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