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From: peterz@infradead.org
To: Chris Down <chris@chrisdown.name>
Cc: Michal Hocko <mhocko@suse.com>, Waiman Long <longman@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [RFC PATCH 0/8] memcg: Enable fine-grained per process memory control
Date: Tue, 18 Aug 2020 12:26:16 +0200	[thread overview]
Message-ID: <20200818102616.GP2674@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200818101756.GA155582@chrisdown.name>

On Tue, Aug 18, 2020 at 11:17:56AM +0100, Chris Down wrote:

> I'd ask that you understand a bit more about the tradeoffs and intentions of
> the patch before rushing in to declare its failure, considering it works
> just fine :-)
> 
> Clamping the maximal time allows the application to take some action to
> remediate the situation, while still being slowed down significantly. 2
> seconds per allocation batch is still absolutely plenty for any use case
> I've come across. If you have evidence it isn't, then present that instead
> of vague notions of "wrongness".

There is no feedback from the freeing rate, therefore it cannot be
correct in maintaining a maximum amount of pages.

0.5 pages / sec is still non-zero, and if the free rate is 0, you'll
crawl across whatever limit was set without any bounds. This is math
101.

It's true that I haven't been paying attention to mm in a while, but I
was one of the original authors of the I/O dirty balancing, I do think I
understand how these things work.

  reply	other threads:[~2020-08-18 10:26 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17 14:08 Waiman Long
2020-08-17 14:08 ` [RFC PATCH 1/8] memcg: Enable fine-grained control of over memory.high action Waiman Long
2020-08-17 14:30   ` Chris Down
2020-08-17 15:38     ` Waiman Long
2020-08-17 16:11       ` Chris Down
2020-08-17 16:44   ` Shakeel Butt
2020-08-17 16:56     ` Chris Down
2020-08-18 19:12       ` Waiman Long
2020-08-18 19:14     ` Waiman Long
2020-08-17 14:08 ` [RFC PATCH 2/8] memcg, mm: Return ENOMEM or delay if memcg_over_limit Waiman Long
2020-08-17 14:08 ` [RFC PATCH 3/8] memcg: Allow the use of task RSS memory as over-high action trigger Waiman Long
2020-08-17 14:08 ` [RFC PATCH 4/8] fs/proc: Support a new procfs memctl file Waiman Long
2020-08-17 14:08 ` [RFC PATCH 5/8] memcg: Allow direct per-task memory limit checking Waiman Long
2020-08-17 14:08 ` [RFC PATCH 6/8] memcg: Introduce additional memory control slowdown if needed Waiman Long
2020-08-17 14:08 ` [RFC PATCH 7/8] memcg: Enable logging of memory control mitigation action Waiman Long
2020-08-17 14:08 ` [RFC PATCH 8/8] memcg: Add over-high action prctl() documentation Waiman Long
2020-08-17 15:26 ` [RFC PATCH 0/8] memcg: Enable fine-grained per process memory control Michal Hocko
2020-08-17 15:55   ` Waiman Long
2020-08-17 19:26     ` Michal Hocko
2020-08-18 19:20       ` Waiman Long
2020-08-18  9:14 ` peterz
2020-08-18  9:26   ` Michal Hocko
2020-08-18  9:59     ` peterz
2020-08-18 10:05       ` Michal Hocko
2020-08-18 10:18         ` peterz
2020-08-18 10:30           ` Michal Hocko
2020-08-18 10:36             ` peterz
2020-08-18 13:49           ` Johannes Weiner
2020-08-21 19:37             ` Peter Zijlstra
2020-08-24 16:58               ` Johannes Weiner
2020-09-07 11:47                 ` Chris Down
2020-09-09 11:53                 ` Michal Hocko
2020-08-18 10:17       ` Chris Down
2020-08-18 10:26         ` peterz [this message]
2020-08-18 10:35           ` Chris Down
2020-08-23  2:49         ` Waiman Long
2020-08-18  9:27   ` Chris Down
2020-08-18 10:04     ` peterz
2020-08-18 12:55       ` Matthew Wilcox
2020-08-20  6:11         ` Dave Chinner
2020-08-18 19:30     ` Waiman Long
2020-08-18 19:27   ` Waiman Long

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