From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrey Ryabinin Subject: =?UTF-8?B?UmU6IOetlOWkjTog562U5aSNOiBbUEFUQ0hdIG1tL21lbWNvbnRyb2wu?= =?UTF-8?Q?c:_speed_up_to_force_empty_a_memory_cgroup?= Date: Wed, 21 Mar 2018 01:35:05 +0300 Message-ID: References: <1521448170-19482-1-git-send-email-lirongqing@baidu.com> <20180319085355.GQ23100@dhcp22.suse.cz> <2AD939572F25A448A3AE3CAEA61328C23745764B@BC-MAIL-M28.internal.baidu.com> <20180319103756.GV23100@dhcp22.suse.cz> <2AD939572F25A448A3AE3CAEA61328C2374589DC@BC-MAIL-M28.internal.baidu.com> <20180320083950.GD23100@dhcp22.suse.cz> <56508bd0-e8d7-55fd-5109-c8dacf26b13e@virtuozzo.com> 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=gamGeXGyujYd0AOpLGqaHQ1E9FW0z4w9y7Nx2ygDzUY=; b=J2Xtoh5/RWmMTwhf2DeNuh404Adu9FIzqqtxI535dyqTNGCieHDhCuQYJSl+yfK/fiIH1eFgKpu0CFFuNEXMTXigLEKapN5chva3jK6lnMVcV12wTIPa/ffIS83KD95fwb/FQ9NQkyy0EnXFeHI50nsF54ERGMHbxhzhzael6aI= In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: David Rientjes Cc: Michal Hocko , "Li,Rongqing" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "cgroups@vger.kernel.org" , "hannes@cmpxchg.org" On 03/21/2018 01:15 AM, David Rientjes wrote: > On Wed, 21 Mar 2018, Andrey Ryabinin wrote: > >>>>> It would probably be best to limit the >>>>> nr_pages to the amount that needs to be reclaimed, though, rather than >>>>> over reclaiming. >>>> >>>> How do you achieve that? The charging path is not synchornized with the >>>> shrinking one at all. >>>> >>> >>> The point is to get a better guess at how many pages, up to >>> SWAP_CLUSTER_MAX, that need to be reclaimed instead of 1. >>> >>>>> If you wanted to be invasive, you could change page_counter_limit() to >>>>> return the count - limit, fix up the callers that look for -EBUSY, and >>>>> then use max(val, SWAP_CLUSTER_MAX) as your nr_pages. >>>> >>>> I am not sure I understand >>>> >>> >>> Have page_counter_limit() return the number of pages over limit, i.e. >>> count - limit, since it compares the two anyway. Fix up existing callers >>> and then clamp that value to SWAP_CLUSTER_MAX in >>> mem_cgroup_resize_limit(). It's a more accurate guess than either 1 or >>> 1024. >>> >> >> JFYI, it's never 1, it's always SWAP_CLUSTER_MAX. >> See try_to_free_mem_cgroup_pages(): >> .... >> struct scan_control sc = { >> .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), >> > > Is SWAP_CLUSTER_MAX the best answer if I'm lowering the limit by 1GB? > Absolutely not. I completely on your side here. I've tried to fix this recently - http://lkml.kernel.org/r/20180119132544.19569-2-aryabinin@virtuozzo.com I guess that Andrew decided to not take my patch, because Michal wasn't happy about it (see mail archives if you want more details).