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[37.188.130.62]) by smtp.gmail.com with ESMTPSA id a9sm6489202wmm.38.2020.04.29.02.04.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2020 02:04:38 -0700 (PDT) Date: Wed, 29 Apr 2020 11:04:37 +0200 From: Michal Hocko To: Vlastimil Babka Cc: David Rientjes , Tetsuo Handa , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman Subject: Re: [patch] mm, oom: stop reclaiming if GFP_ATOMIC will start failing soon Message-ID: <20200429090437.GX28637@dhcp22.suse.cz> References: <20200425172706.26b5011293e8dc77b1dccaf3@linux-foundation.org> <20200427133051.b71f961c1bc53a8e72c4f003@linux-foundation.org> <28e35a8b-400e-9320-5a97-accfccf4b9a8@suse.cz> <31f1f84d-c5fe-824b-3c28-1a9ad69fcae5@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <31f1f84d-c5fe-824b-3c28-1a9ad69fcae5@suse.cz> 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 Wed 29-04-20 09:51:39, Vlastimil Babka wrote: > On 4/28/20 11:48 PM, David Rientjes wrote: > > On Tue, 28 Apr 2020, Vlastimil Babka wrote: > > > > Yes, order-0 reclaim capture is interesting since the issue being reported > > here is userspace going out to lunch because it loops for an unbounded > > amount of time trying to get above a watermark where it's allowed to > > allocate and other consumers are depleting that resource. > > > > We actually prefer to oom kill earlier rather than being put in a > > perpetual state of aggressive reclaim that affects all allocators and the > > unbounded nature of those allocations leads to very poor results for > > everybody. > > Sure. My vague impression is that your (and similar cloud companies) kind of > workloads are designed to maximize machine utilization, and overshooting and > killing something as a result is no big deal. Then you perhaps have more > probability of hitting this state, and on the other hand, even an occasional > premature oom kill is not a big deal? > > My concers are workloads not designed in such a way, where premature oom kill > due to temporary higher reclaim activity together with burst of incoming network > packets will result in e.g. killing an important database. There, the tradeoff > looks different. Completely agreed! The in kernel OOM killer is to deal with situations when memory is desperately depleted without any sign of a forward progress. If there is a reclaimable memory then we are not there yet. If a workload can benefit from early oom killing based on response time then we have facilities to achieve that (e.g. PSI). -- Michal Hocko SUSE Labs