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[209.85.220.65]) by mx.google.com with SMTPS id y127sor4500814ywf.195.2019.01.28.13.42.15 for (Google Transport Security); Mon, 28 Jan 2019 13:42:16 -0800 (PST) Received-SPF: pass (google.com: domain of chris@chrisdown.name designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@chrisdown.name header.s=google header.b=QWvsOqRq; spf=pass (google.com: domain of chris@chrisdown.name designates 209.85.220.65 as permitted sender) smtp.mailfrom=chris@chrisdown.name; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chrisdown.name DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=a9PsKmGgPsTKkLBb3g/jY5/HxZPgchB4hPGH18bC0Lo=; b=QWvsOqRqyIcKZR7jItEvBi0genFdYcFV76xiW7vN4DO4Eba+BvzpUc474b40EBe4es h4O385MUeLovYQGLyM9wvEI2R3H0Lshq64jenrQ1csimCipZwR+Ux6IUPGUTgHM8Jw5f 0a2oM0SqHJFVbknYw26SZ8N4D2DVfzvcaDunk= X-Google-Smtp-Source: ALg8bN7ixIYyq/jqwUusdxnjFTjdORjTiX7RCaORCK6XnS2wV8OmW/M/daK2UKZbt4qlEjcxYyGVhw== X-Received: by 2002:a81:87c3:: with SMTP id x186mr22526821ywf.147.1548711735622; Mon, 28 Jan 2019 13:42:15 -0800 (PST) Received: from localhost ([2620:10d:c091:200::7:aa7d]) by smtp.gmail.com with ESMTPSA id f10sm19386715ywb.26.2019.01.28.13.42.14 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 28 Jan 2019 13:42:14 -0800 (PST) Date: Mon, 28 Jan 2019 16:42:13 -0500 From: Chris Down To: Roman Gushchin Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Tejun Heo , Dennis Zhou , "linux-kernel@vger.kernel.org" , "cgroups@vger.kernel.org" , "linux-mm@kvack.org" , Kernel Team Subject: Re: [PATCH] mm: Proportional memory.{low,min} reclaim Message-ID: <20190128214213.GB15349@chrisdown.name> References: <20190124014455.GA6396@chrisdown.name> <20190128210031.GA31446@castle.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190128210031.GA31446@castle.DHCP.thefacebook.com> User-Agent: Mutt/1.11.2 (2019-01-07) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Roman Gushchin writes: >Hm, it looks a bit suspicious to me. > >Let's say memory.low = 3G, memory.min = 1G and memory.current = 2G. >cgroup_size / protection == 1, so scan doesn't depend on memory.min at all. > >So, we need to look directly at memory.emin in memcg_low_reclaim case, and >ignore memory.(e)low. Hmm, this isn't really a common situation that I'd thought about, but it seems reasonable to make the boundaries when in low reclaim to be between min and low, rather than 0 and low. I'll add another patch with that. Thanks >> + scan = clamp(scan, SWAP_CLUSTER_MAX, lruvec_size); > >Idk, how much sense does it have to make it larger than SWAP_CLUSTER_MAX, >given that it will become 0 on default (and almost any other) priority. In my testing, setting the scan target to 0 and thus reducing scope for reclaim can result in increasing the scan priority more than is desirable, and since we base some vm heuristics based on that, that seemed concerning. I'd rather start being a bit more cautious, erring on the side of scanning at least some pages from this memcg when priority gets elevated. Thanks for the review!