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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 [100.121.56.177] (unknown [213.205.240.53]) (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 1A2EB1C02183; Thu, 8 Aug 2019 16:10:09 +0100 (BST) Date: Thu, 08 Aug 2019 16:10:07 +0100 User-Agent: K-9 Mail for Android In-Reply-To: <20190808114826.GC18351@dhcp22.suse.cz> References: <20190805193148.GB4128@cmpxchg.org> <398f31f3-0353-da0c-fc54-643687bb4774@suse.cz> <20190806142728.GA12107@cmpxchg.org> <20190806143608.GE11812@dhcp22.suse.cz> <20190806220150.GA22516@cmpxchg.org> <20190807075927.GO11812@dhcp22.suse.cz> <20190807205138.GA24222@cmpxchg.org> <20190808114826.GC18351@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 ,Johannes Weiner CC: Suren Baghdasaryan ,Vlastimil Babka ,"Artem S. Tashkinov" ,Andrew Morton ,LKML ,linux-mm From: ndrw.xf@redhazel.co.uk Message-ID: <806F5696-A8D6-481D-A82F-49DEC1F2B035@redhazel.co.uk> 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 8 August 2019 12:48:26 BST, Michal Hocko wrote: >>=20 >> Per default, the OOM killer will engage after 15 seconds of at least >> 80% memory pressure=2E These values are tunable via sysctls >> vm=2Ethrashing_oom_period and vm=2Ethrashing_oom_level=2E > >As I've said earlier I would be somehow more comfortable with a kernel >command line/module parameter based tuning because it is less of a >stable API and potential future stall detector might be completely >independent on PSI and the current metric exported=2E But I can live with >that because a period and level sounds quite generic=2E Would it be possible to reserve a fixed (configurable) amount of RAM for c= aches, and trigger OOM killer earlier, before most UI code is evicted from = memory? In my use case, I am happy sacrificing e=2Eg=2E 0=2E5GB and kill ru= naway tasks _before_ the system freezes=2E Potentially OOM killer would als= o work better in such conditions=2E I almost never work at close to full me= mory capacity, it's always a single task that goes wrong and brings the sys= tem down=2E The problem with PSI sensing is that it works after the fact (after the fr= eeze has already occurred)=2E It is not very different from issuing SysRq-f= manually on a frozen system, although it would still be a handy feature fo= r batched tasks and remote access=2E=20 Best regards,=20 ndrw