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Authentication-Results: mx.google.com; spf=pass (google.com: domain of ndrw.xf@redhazel.co.uk designates 68.66.241.172 as permitted sender) smtp.mailfrom=ndrw.xf@redhazel.co.uk Received: from [192.168.1.66] (unknown [212.159.68.143]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by vps.redhazel.co.uk (Postfix) with ESMTPSA id 1E5011C02B32; Sat, 10 Aug 2019 22:07:50 +0100 (BST) Subject: Re: Let's talk about the elephant in the room - the Linux kernel's inability to gracefully handle low memory pressure To: Michal Hocko Cc: Johannes Weiner , Suren Baghdasaryan , Vlastimil Babka , "Artem S. Tashkinov" , Andrew Morton , LKML , linux-mm References: <20190806220150.GA22516@cmpxchg.org> <20190807075927.GO11812@dhcp22.suse.cz> <20190807205138.GA24222@cmpxchg.org> <20190808114826.GC18351@dhcp22.suse.cz> <806F5696-A8D6-481D-A82F-49DEC1F2B035@redhazel.co.uk> <20190808163228.GE18351@dhcp22.suse.cz> <5FBB0A26-0CFE-4B88-A4F2-6A42E3377EDB@redhazel.co.uk> <20190808185925.GH18351@dhcp22.suse.cz> <08e5d007-a41a-e322-5631-b89978b9cc20@redhazel.co.uk> <20190809085748.GN18351@dhcp22.suse.cz> From: ndrw Message-ID: <5fcf237c-d270-26e5-e995-02755695b459@redhazel.co.uk> Date: Sat, 10 Aug 2019 22:07:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190809085748.GN18351@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US 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 09/08/2019 09:57, Michal Hocko wrote: > This is a useful feedback! What was your workload? Which kernel version? With 16GB zram swap and swappiness=60 I get the avg10 memory PSI numbers of about 10 when swap is half filled and ~30 immediately before the freeze. Swapping with zram has less effect on system responsiveness comparing to swapping to an ssd, so, if combined with the proposed PSI triggered OOM killer, this could be a viable solution. Still, using swap only to make PSI sensing work when triggering OOM killer at non-zero available memory would do the job just as well is a bit of an overkill. I don't really need these extra few GB or memory, just want to get rid of system freezes. Perhaps we could have both heuristics. Best regards, ndrw