From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrey Ryabinin Subject: Re: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Date: Mon, 15 Jan 2018 15:53:35 +0300 Message-ID: <17c368ce-3a20-d776-bc11-65b6a5bb1ff7@virtuozzo.com> References: <20180109152622.31ca558acb0cc25a1b14f38c@linux-foundation.org> <20180110124317.28887-1-aryabinin@virtuozzo.com> <20180111104239.GZ1732@dhcp22.suse.cz> <4a8f667d-c2ae-e3df-00fd-edc01afe19e1@virtuozzo.com> <20180111124629.GA1732@dhcp22.suse.cz> <20180111162947.GG1732@dhcp22.suse.cz> <560a77b5-02d7-cbae-35f3-0b20a1c384c2@virtuozzo.com> <20180112122405.GK1732@dhcp22.suse.cz> <7d1b5bfb-f602-8cf4-2de6-dd186484e55c@virtuozzo.com> <20180115124652.GB22473@dhcp22.suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=virtuozzo.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=j+z8BfABAWbTJZUr1p3JjRAj2O+MLVUormZqfjIcyhI=; b=HrHOeuCKZ1wxMQEZXAqOm9kVaBz9t815GmBXWc26I7r9WqFfW7BEnL+ll2yJTC0KOCvbQ0EmOQ34do6EZZVo+rD+7YnwP3zkVYJpYx5SH1byFKTX3tPrR9+QtiWWpNwGcbvjsEmk89nECQLmm68O70KRSyh5B/zOH5cs9Xz3DC4= In-Reply-To: <20180115124652.GB22473@dhcp22.suse.cz> Content-Language: en-US Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt On 01/15/2018 03:46 PM, Michal Hocko wrote: > On Mon 15-01-18 15:30:59, Andrey Ryabinin wrote: >> >> >> On 01/12/2018 03:24 PM, Michal Hocko wrote: >>> On Fri 12-01-18 00:59:38, Andrey Ryabinin wrote: >>>> On 01/11/2018 07:29 PM, Michal Hocko wrote: >>> [...] >>>>> I do not think so. Consider that this reclaim races with other >>>>> reclaimers. Now you are reclaiming a large chunk so you might end up >>>>> reclaiming more than necessary. SWAP_CLUSTER_MAX would reduce the over >>>>> reclaim to be negligible. >>>>> >>>> >>>> I did consider this. And I think, I already explained that sort of race in previous email. >>>> Whether "Task B" is really a task in cgroup or it's actually a bunch of reclaimers, >>>> doesn't matter. That doesn't change anything. >>> >>> I would _really_ prefer two patches here. The first one removing the >>> hard coded reclaim count. That thing is just dubious at best. If you >>> _really_ think that the higher reclaim target is meaningfull then make >>> it a separate patch. I am not conviced but I will not nack it it either. >>> But it will make our life much easier if my over reclaim concern is >>> right and we will need to revert it. Conceptually those two changes are >>> independent anywa. >>> >> >> Ok, fair point. But what about livelock than? Don't you think that we should >> go back to something like in V1 patch to prevent it? > > I am not sure what do you mean by the livelock here. > Livelock is when tasks in cgroup constantly allocate reclaimable memory at high rate, and user asked to set too low unreachable limit e.g. 'echo 4096 > memory.limit_in_bytes'. We will loop indefinitely in mem_cgroup_resize_limit(), because try_to_free_mem_cgroup_pages() != 0 (as long as cgroup tasks generate new reclaimable pages fast enough). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org