From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-team-b10kYP2dOMg@public.gmane.org
Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high
Date: Wed, 19 Feb 2020 11:31:39 -0800 [thread overview]
Message-ID: <20200219113139.ee60838bc7eb35747eb330fa@linux-foundation.org> (raw)
In-Reply-To: <20200219183731.GC11847-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
On Wed, 19 Feb 2020 19:37:31 +0100 Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> On Wed 19-02-20 13:12:19, Johannes Weiner wrote:
> > We have received regression reports from users whose workloads moved
> > into containers and subsequently encountered new latencies. For some
> > users these were a nuisance, but for some it meant missing their SLA
> > response times. We tracked those delays down to cgroup limits, which
> > inject direct reclaim stalls into the workload where previously all
> > reclaim was handled my kswapd.
>
> I am curious why is this unexpected when the high limit is explicitly
> documented as a throttling mechanism.
Yes, this sounds like a feature-not-a-bug.
But what was the nature of these stalls? If they were "stuck in D
state waiting for something" then that's throttling. If they were
"unexpected bursts of in-kernel CPU activity" then I see a better case.
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
Roman Gushchin <guro@fb.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high
Date: Wed, 19 Feb 2020 11:31:39 -0800 [thread overview]
Message-ID: <20200219113139.ee60838bc7eb35747eb330fa@linux-foundation.org> (raw)
In-Reply-To: <20200219183731.GC11847@dhcp22.suse.cz>
On Wed, 19 Feb 2020 19:37:31 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> On Wed 19-02-20 13:12:19, Johannes Weiner wrote:
> > We have received regression reports from users whose workloads moved
> > into containers and subsequently encountered new latencies. For some
> > users these were a nuisance, but for some it meant missing their SLA
> > response times. We tracked those delays down to cgroup limits, which
> > inject direct reclaim stalls into the workload where previously all
> > reclaim was handled my kswapd.
>
> I am curious why is this unexpected when the high limit is explicitly
> documented as a throttling mechanism.
Yes, this sounds like a feature-not-a-bug.
But what was the nature of these stalls? If they were "stuck in D
state waiting for something" then that's throttling. If they were
"unexpected bursts of in-kernel CPU activity" then I see a better case.
next prev parent reply other threads:[~2020-02-19 19:31 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 18:12 [PATCH] mm: memcontrol: asynchronous reclaim for memory.high Johannes Weiner
2020-02-19 18:12 ` Johannes Weiner
[not found] ` <20200219181219.54356-1-hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
2020-02-19 18:37 ` Michal Hocko
2020-02-19 18:37 ` Michal Hocko
[not found] ` <20200219183731.GC11847-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-02-19 19:16 ` Johannes Weiner
2020-02-19 19:16 ` Johannes Weiner
[not found] ` <20200219191618.GB54486-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
2020-02-19 19:53 ` Michal Hocko
2020-02-19 19:53 ` Michal Hocko
2020-02-19 21:17 ` Johannes Weiner
[not found] ` <20200219211735.GD54486-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
2020-02-20 9:46 ` Michal Hocko
2020-02-20 9:46 ` Michal Hocko
[not found] ` <20200220094639.GD20509-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-02-20 14:41 ` Johannes Weiner
2020-02-20 14:41 ` Johannes Weiner
[not found] ` <20200219195332.GE11847-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-02-19 21:41 ` Daniel Jordan
2020-02-19 21:41 ` Daniel Jordan
[not found] ` <20200219214112.4kt573kyzbvmbvn3-S51bK0XF4qpuJJETbFA3a0B3C2bhBk7L0E9HWUfgJXw@public.gmane.org>
2020-02-19 22:08 ` Johannes Weiner
2020-02-19 22:08 ` Johannes Weiner
[not found] ` <20200219220859.GF54486-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
2020-02-20 15:45 ` Daniel Jordan
2020-02-20 15:45 ` Daniel Jordan
[not found] ` <20200220154524.dql3i5brnjjwecft-S51bK0XF4qpuJJETbFA3a0B3C2bhBk7L0E9HWUfgJXw@public.gmane.org>
2020-02-20 15:56 ` Tejun Heo
2020-02-20 15:56 ` Tejun Heo
[not found] ` <20200220155651.GG698990-146+VewaZzwNjtGbbfXrCEEOCMrvLtNR@public.gmane.org>
2020-02-20 18:23 ` Daniel Jordan
2020-02-20 18:23 ` Daniel Jordan
[not found] ` <20200220182326.ubcjycaubgykiy6e-S51bK0XF4qpuJJETbFA3a0B3C2bhBk7L0E9HWUfgJXw@public.gmane.org>
2020-02-20 18:45 ` Tejun Heo
2020-02-20 18:45 ` Tejun Heo
[not found] ` <20200220184545.GH698990-146+VewaZzwNjtGbbfXrCEEOCMrvLtNR@public.gmane.org>
2020-02-20 19:55 ` Daniel Jordan
2020-02-20 19:55 ` Daniel Jordan
[not found] ` <20200220195535.7xblt45akld6eftj-S51bK0XF4qpuJJETbFA3a0B3C2bhBk7L0E9HWUfgJXw@public.gmane.org>
2020-02-20 20:54 ` Tejun Heo
2020-02-20 20:54 ` Tejun Heo
2020-02-19 19:17 ` Chris Down
2020-02-19 19:17 ` Chris Down
2020-02-19 19:31 ` Andrew Morton [this message]
2020-02-19 19:31 ` Andrew Morton
2020-02-19 21:33 ` Johannes Weiner
2020-02-26 20:25 ` Shakeel Butt
2020-02-26 20:25 ` Shakeel Butt
[not found] ` <CALvZod7fya+o8mO+qo=FXjk3WgNje=2P=sxM5StgdBoGNeXRMg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-02-26 22:26 ` Johannes Weiner
2020-02-26 22:26 ` Johannes Weiner
[not found] ` <20200226222642.GB30206-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
2020-02-26 23:36 ` Shakeel Butt
2020-02-26 23:36 ` Shakeel Butt
2020-02-26 23:46 ` Johannes Weiner
2020-02-27 0:12 ` Yang Shi
2020-02-27 0:12 ` Yang Shi
[not found] ` <2be6ac8d-e290-0a85-5cfa-084968a7fe36-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
2020-02-27 2:42 ` Shakeel Butt
2020-02-27 2:42 ` Shakeel Butt
2020-02-27 9:58 ` Michal Hocko
2020-02-27 9:58 ` Michal Hocko
2020-02-27 12:50 ` Johannes Weiner
2020-02-27 12:50 ` Johannes Weiner
2020-02-26 23:59 ` Yang Shi
2020-02-26 23:59 ` Yang Shi
2020-02-27 2:36 ` Shakeel Butt
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