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[104.47.1.136]) by mx.google.com with ESMTPS id h70si13134749pfc.186.2017.12.20.05.17.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 20 Dec 2017 05:17:54 -0800 (PST) From: Andrey Ryabinin Subject: [PATCH v2 1/2] mm/memcg: try harder to decrease [memory,memsw].limit_in_bytes Date: Wed, 20 Dec 2017 16:21:13 +0300 Message-Id: <20171220132114.6883-1-aryabinin@virtuozzo.com> In-Reply-To: <20171220102429.31601-1-aryabinin@virtuozzo.com> References: <20171220102429.31601-1-aryabinin@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 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 trying to free required amount of pages until reclaimer makes any progress. Signed-off-by: Andrey Ryabinin --- mm/memcontrol.c | 70 +++++++++++++-------------------------------------------- 1 file changed, 16 insertions(+), 54 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f40b5ad3f959..0d26db9a665d 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) @@ -2462,22 +2448,10 @@ static DEFINE_MUTEX(memcg_limit_mutex); static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, unsigned long limit) { - unsigned long curusage; - unsigned long oldusage; + unsigned long usage; bool enlarge = false; - int retry_count; int ret; - /* - * 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(&memcg->memory); - do { if (signal_pending(current)) { ret = -EINTR; @@ -2498,15 +2472,13 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, if (!ret) break; - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, true); - - curusage = page_counter_read(&memcg->memory); - /* Usage is reduced ? */ - if (curusage >= oldusage) - retry_count--; - else - oldusage = curusage; - } while (retry_count); + usage = page_counter_read(&memcg->memory); + if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, + GFP_KERNEL, true)) { + ret = -EBUSY; + break; + } + } while (true); if (!ret && enlarge) memcg_oom_recover(memcg); @@ -2517,18 +2489,10 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg, unsigned long limit) { - unsigned long curusage; - unsigned long oldusage; + unsigned long usage; bool enlarge = false; - int retry_count; int ret; - /* see mem_cgroup_resize_res_limit */ - retry_count = MEM_CGROUP_RECLAIM_RETRIES * - mem_cgroup_count_children(memcg); - - oldusage = page_counter_read(&memcg->memsw); - do { if (signal_pending(current)) { ret = -EINTR; @@ -2549,15 +2513,13 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg, if (!ret) break; - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, false); - - curusage = page_counter_read(&memcg->memsw); - /* Usage is reduced ? */ - if (curusage >= oldusage) - retry_count--; - else - oldusage = curusage; - } while (retry_count); + usage = page_counter_read(&memcg->memsw); + if (!try_to_free_mem_cgroup_pages(memcg, usage - limit, + GFP_KERNEL, false)) { + 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