From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 825926B0266 for ; Thu, 11 Jan 2018 07:46:32 -0500 (EST) Received: by mail-wr0-f200.google.com with SMTP id q4so1433401wre.14 for ; Thu, 11 Jan 2018 04:46:32 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 37si6169156wrb.8.2018.01.11.04.46.31 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 11 Jan 2018 04:46:31 -0800 (PST) Date: Thu, 11 Jan 2018 13:46:29 +0100 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: 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/ . Don't email: email@kvack.org