From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934239AbeAKMqd (ORCPT + 1 other); Thu, 11 Jan 2018 07:46:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:44358 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752735AbeAKMqb (ORCPT ); Thu, 11 Jan 2018 07:46:31 -0500 Date: Thu, 11 Jan 2018 13:46:29 +0100 From: Michal Hocko To: Andrey Ryabinin Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt Subject: Re: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Message-ID: <20180111124629.GA1732@dhcp22.suse.cz> References: <20180109152622.31ca558acb0cc25a1b14f38c@linux-foundation.org> <20180110124317.28887-1-aryabinin@virtuozzo.com> <20180111104239.GZ1732@dhcp22.suse.cz> <4a8f667d-c2ae-e3df-00fd-edc01afe19e1@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4a8f667d-c2ae-e3df-00fd-edc01afe19e1@virtuozzo.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Thu 11-01-18 15:21:33, Andrey Ryabinin wrote: > > > On 01/11/2018 01:42 PM, Michal Hocko wrote: > > On Wed 10-01-18 15:43:17, Andrey Ryabinin wrote: > > [...] > >> @@ -2506,15 +2480,13 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, > >> if (!ret) > >> break; > >> > >> - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, !memsw); > >> - > >> - curusage = page_counter_read(counter); > >> - /* Usage is reduced ? */ > >> - if (curusage >= oldusage) > >> - retry_count--; > >> - else > >> - oldusage = curusage; > >> - } while (retry_count); > >> + usage = page_counter_read(counter); > >> + if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, > >> + GFP_KERNEL, !memsw)) { > > > > If the usage drops below limit in the meantime then you get underflow > > and reclaim the whole memcg. I do not think this is a good idea. This > > can also lead to over reclaim. Why don't you simply stick with the > > original SWAP_CLUSTER_MAX (aka 1 for try_to_free_mem_cgroup_pages)? > > > > Because, if new limit is gigabytes bellow the current usage, retrying to set > new limit after reclaiming only 32 pages seems unreasonable. Who would do insanity like that? > @@ -2487,8 +2487,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, > if (!ret) > break; > > - usage = page_counter_read(counter); > - if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, > + nr_pages = max_t(long, 1, page_counter_read(counter) - limit); > + if (!try_to_free_mem_cgroup_pages(memcg, nr_pages, > GFP_KERNEL, !memsw)) { > ret = -EBUSY; > break; How does this address the over reclaim concern? -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Date: Thu, 11 Jan 2018 13:46:29 +0100 Message-ID: <20180111124629.GA1732@dhcp22.suse.cz> References: <20180109152622.31ca558acb0cc25a1b14f38c@linux-foundation.org> <20180110124317.28887-1-aryabinin@virtuozzo.com> <20180111104239.GZ1732@dhcp22.suse.cz> <4a8f667d-c2ae-e3df-00fd-edc01afe19e1@virtuozzo.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <4a8f667d-c2ae-e3df-00fd-edc01afe19e1@virtuozzo.com> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andrey Ryabinin Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt On Thu 11-01-18 15:21:33, Andrey Ryabinin wrote: > > > On 01/11/2018 01:42 PM, Michal Hocko wrote: > > On Wed 10-01-18 15:43:17, Andrey Ryabinin wrote: > > [...] > >> @@ -2506,15 +2480,13 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, > >> if (!ret) > >> break; > >> > >> - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, !memsw); > >> - > >> - curusage = page_counter_read(counter); > >> - /* Usage is reduced ? */ > >> - if (curusage >= oldusage) > >> - retry_count--; > >> - else > >> - oldusage = curusage; > >> - } while (retry_count); > >> + usage = page_counter_read(counter); > >> + if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, > >> + GFP_KERNEL, !memsw)) { > > > > If the usage drops below limit in the meantime then you get underflow > > and reclaim the whole memcg. I do not think this is a good idea. This > > can also lead to over reclaim. Why don't you simply stick with the > > original SWAP_CLUSTER_MAX (aka 1 for try_to_free_mem_cgroup_pages)? > > > > Because, if new limit is gigabytes bellow the current usage, retrying to set > new limit after reclaiming only 32 pages seems unreasonable. Who would do insanity like that? > @@ -2487,8 +2487,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, > if (!ret) > break; > > - usage = page_counter_read(counter); > - if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, > + nr_pages = max_t(long, 1, page_counter_read(counter) - limit); > + if (!try_to_free_mem_cgroup_pages(memcg, nr_pages, > GFP_KERNEL, !memsw)) { > ret = -EBUSY; > break; How does this address the over reclaim concern? -- Michal Hocko SUSE Labs -- 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/ . 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