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Tue, 18 Aug 2020 10:26:18 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 09548300DB4; Tue, 18 Aug 2020 12:26:17 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E60632B76E7C6; Tue, 18 Aug 2020 12:26:16 +0200 (CEST) Date: Tue, 18 Aug 2020 12:26:16 +0200 From: peterz@infradead.org To: Chris Down Cc: Michal Hocko , Waiman Long , Andrew Morton , Johannes Weiner , Vladimir Davydov , Jonathan Corbet , Alexey Dobriyan , Ingo Molnar , Juri Lelli , Vincent Guittot , 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 Message-ID: <20200818102616.GP2674@hirez.programming.kicks-ass.net> References: <20200817140831.30260-1-longman@redhat.com> <20200818091453.GL2674@hirez.programming.kicks-ass.net> <20200818092617.GN28270@dhcp22.suse.cz> <20200818095910.GM2674@hirez.programming.kicks-ass.net> <20200818101756.GA155582@chrisdown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200818101756.GA155582@chrisdown.name> X-Rspamd-Queue-Id: 509CA18038E68 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.