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From: Michal Hocko <mhocko@kernel.org>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Shakeel Butt <shakeelb@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Roman Gushchin <guro@fb.com>,
	Linux MM <linux-mm@kvack.org>, Cgroups <cgroups@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high
Date: Thu, 27 Feb 2020 10:58:59 +0100	[thread overview]
Message-ID: <20200227095859.GA3771@dhcp22.suse.cz> (raw)
In-Reply-To: <2be6ac8d-e290-0a85-5cfa-084968a7fe36@linux.alibaba.com>

On Wed 26-02-20 16:12:23, Yang Shi wrote:
[...]
> Actually I'm wondering if we really need account CPU cycles used by
> background reclaimer or not. For our usecase (this may be not general), the
> purpose of background reclaimer is to avoid latency sensitive workloads get
> into direct relcaim (avoid the stall from direct relcaim). In fact it just
> "steal" CPU cycles from lower priority or best-effort workloads to guarantee
> latency sensitive workloads behave well. If the "stolen" CPU cycles are
> accounted, it means the latency sensitive workloads would get throttled from
> somewhere else later, i.e. by CPU share.

I believe we need to because that work is not for free and so you are
essentially stealing those CPUs cycles from everybody else outside of
your throttled cgroup.
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Yang Shi <yang.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>,
	Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Kernel Team <kernel-team-b10kYP2dOMg@public.gmane.org>
Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high
Date: Thu, 27 Feb 2020 10:58:59 +0100	[thread overview]
Message-ID: <20200227095859.GA3771@dhcp22.suse.cz> (raw)
In-Reply-To: <2be6ac8d-e290-0a85-5cfa-084968a7fe36-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>

On Wed 26-02-20 16:12:23, Yang Shi wrote:
[...]
> Actually I'm wondering if we really need account CPU cycles used by
> background reclaimer or not. For our usecase (this may be not general), the
> purpose of background reclaimer is to avoid latency sensitive workloads get
> into direct relcaim (avoid the stall from direct relcaim). In fact it just
> "steal" CPU cycles from lower priority or best-effort workloads to guarantee
> latency sensitive workloads behave well. If the "stolen" CPU cycles are
> accounted, it means the latency sensitive workloads would get throttled from
> somewhere else later, i.e. by CPU share.

I believe we need to because that work is not for free and so you are
essentially stealing those CPUs cycles from everybody else outside of
your throttled cgroup.
-- 
Michal Hocko
SUSE Labs

  parent reply	other threads:[~2020-02-27  9:59 UTC|newest]

Thread overview: 56+ 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
2020-02-19 18:37 ` Michal Hocko
2020-02-19 18:37   ` Michal Hocko
2020-02-19 19:16   ` Johannes Weiner
2020-02-19 19:16     ` Johannes Weiner
2020-02-19 19:53     ` Michal Hocko
2020-02-19 19:53       ` Michal Hocko
2020-02-19 21:17       ` Johannes Weiner
2020-02-20  9:46         ` Michal Hocko
2020-02-20  9:46           ` Michal Hocko
2020-02-20 14:41           ` Johannes Weiner
2020-02-20 14:41             ` Johannes Weiner
2020-02-19 21:41       ` Daniel Jordan
2020-02-19 21:41         ` Daniel Jordan
2020-02-19 22:08         ` Johannes Weiner
2020-02-19 22:08           ` Johannes Weiner
2020-02-20 15:45           ` Daniel Jordan
2020-02-20 15:45             ` Daniel Jordan
2020-02-20 15:56             ` Tejun Heo
2020-02-20 15:56               ` Tejun Heo
2020-02-20 18:23               ` Daniel Jordan
2020-02-20 18:23                 ` Daniel Jordan
2020-02-20 18:45                 ` Tejun Heo
2020-02-20 18:45                   ` Tejun Heo
2020-02-20 19:55                   ` Daniel Jordan
2020-02-20 19:55                     ` Daniel Jordan
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
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
2020-02-26 20:25   ` Shakeel Butt
2020-02-26 22:26   ` Johannes Weiner
2020-02-26 22:26     ` Johannes Weiner
2020-02-26 23:36     ` Shakeel Butt
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
2020-02-27  2:42       ` Shakeel Butt
2020-02-27  2:42         ` Shakeel Butt
2020-02-27  2:42         ` Shakeel Butt
2020-02-27  9:58       ` Michal Hocko [this message]
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
2020-02-27  2:36       ` Shakeel Butt

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