From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 898DB6B0268 for ; Wed, 10 Jan 2018 07:43:26 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id x24so6914245pge.13 for ; Wed, 10 Jan 2018 04:43:26 -0800 (PST) Received: from EUR03-VE1-obe.outbound.protection.outlook.com (mail-eopbgr50111.outbound.protection.outlook.com. [40.107.5.111]) by mx.google.com with ESMTPS id a23si11703389pfa.111.2018.01.10.04.43.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 10 Jan 2018 04:43:24 -0800 (PST) From: Andrey Ryabinin Subject: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Date: Wed, 10 Jan 2018 15:43:17 +0300 Message-Id: <20180110124317.28887-1-aryabinin@virtuozzo.com> In-Reply-To: <20180109152622.31ca558acb0cc25a1b14f38c@linux-foundation.org> References: <20180109152622.31ca558acb0cc25a1b14f38c@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shakeel Butt , Andrey Ryabinin mem_cgroup_resize_[memsw]_limit() tries to free only 32 (SWAP_CLUSTER_MAX) pages on each iteration. This makes practically impossible to decrease limit of memory cgroup. Tasks could easily allocate back 32 pages, so we can't reduce memory usage, and once retry_count reaches zero we return -EBUSY. Easy to reproduce the problem by running the following commands: mkdir /sys/fs/cgroup/memory/test echo $$ >> /sys/fs/cgroup/memory/test/tasks cat big_file > /dev/null & sleep 1 && echo $((100*1024*1024)) > /sys/fs/cgroup/memory/test/memory.limit_in_bytes -bash: echo: write error: Device or resource busy Instead of relying on retry_count, keep retrying the reclaim until the desired limit is reached or fail if the reclaim doesn't make any progress or a signal is pending. Signed-off-by: Andrey Ryabinin Reviewed-by: Shakeel Butt --- Changes since v3: - Rebase Changes since v2: - Changelog wording per mhocko@ mm/memcontrol.c | 44 ++++++++------------------------------------ 1 file changed, 8 insertions(+), 36 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 13aeccf32c2e..c3d1eaef752d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1176,20 +1176,6 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p) } /* - * This function returns the number of memcg under hierarchy tree. Returns - * 1(self count) if no children. - */ -static int mem_cgroup_count_children(struct mem_cgroup *memcg) -{ - int num = 0; - struct mem_cgroup *iter; - - for_each_mem_cgroup_tree(iter, memcg) - num++; - return num; -} - -/* * Return the memory (and swap, if configured) limit for a memcg. */ unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg) @@ -2462,24 +2448,12 @@ static DEFINE_MUTEX(memcg_limit_mutex); static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, unsigned long limit, bool memsw) { - unsigned long curusage; - unsigned long oldusage; + unsigned long usage; bool enlarge = false; - int retry_count; int ret; bool limits_invariant; struct page_counter *counter = memsw ? &memcg->memsw : &memcg->memory; - /* - * For keeping hierarchical_reclaim simple, how long we should retry - * is depends on callers. We set our retry-count to be function - * of # of children which we should visit in this loop. - */ - retry_count = MEM_CGROUP_RECLAIM_RETRIES * - mem_cgroup_count_children(memcg); - - oldusage = page_counter_read(counter); - do { if (signal_pending(current)) { ret = -EINTR; @@ -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)) { + ret = -EBUSY; + break; + } + } while (true); if (!ret && enlarge) memcg_oom_recover(memcg); -- 2.13.6 -- 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