From 0a4465d340282f92719f4e3a56545a848e638d15 Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Fri, 17 Aug 2018 15:47:37 -0700 Subject: mm, memcg: assign memcg-aware shrinkers bitmap to memcg Imagine a big node with many cpus, memory cgroups and containers. Let we have 200 containers, every container has 10 mounts, and 10 cgroups. All container tasks don't touch foreign containers mounts. If there is intensive pages write, and global reclaim happens, a writing task has to iterate over all memcgs to shrink slab, before it's able to go to shrink_page_list(). Iteration over all the memcg slabs is very expensive: the task has to visit 200 * 10 = 2000 shrinkers for every memcg, and since there are 2000 memcgs, the total calls are 2000 * 2000 = 4000000. So, the shrinker makes 4 million do_shrink_slab() calls just to try to isolate SWAP_CLUSTER_MAX pages in one of the actively writing memcg via shrink_page_list(). I've observed a node spending almost 100% in kernel, making useless iteration over already shrinked slab. This patch adds bitmap of memcg-aware shrinkers to memcg. The size of the bitmap depends on bitmap_nr_ids, and during memcg life it's maintained to be enough to fit bitmap_nr_ids shrinkers. Every bit in the map is related to corresponding shrinker id. Next patches will maintain set bit only for really charged memcg. This will allow shrink_slab() to increase its performance in significant way. See the last patch for the numbers. [ktkhai@virtuozzo.com: v9] Link: http://lkml.kernel.org/r/153112549031.4097.3576147070498769979.stgit@localhost.localdomain [ktkhai@virtuozzo.com: add comment to mem_cgroup_css_online()] Link: http://lkml.kernel.org/r/521f9e5f-c436-b388-fe83-4dc870bfb489@virtuozzo.com Link: http://lkml.kernel.org/r/153063056619.1818.12550500883688681076.stgit@localhost.localdomain Signed-off-by: Kirill Tkhai Acked-by: Vladimir Davydov Tested-by: Shakeel Butt Cc: Al Viro Cc: Andrey Ryabinin Cc: Chris Wilson Cc: Greg Kroah-Hartman Cc: Guenter Roeck Cc: "Huang, Ying" Cc: Johannes Weiner Cc: Josef Bacik Cc: Li RongQing Cc: Matthew Wilcox Cc: Matthias Kaehlcke Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Philippe Ombredanne Cc: Roman Gushchin Cc: Sahitya Tummala Cc: Stephen Rothwell Cc: Tetsuo Handa Cc: Thomas Gleixner Cc: Waiman Long Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 313355dddf66..827c9e87ca08 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -320,6 +320,119 @@ EXPORT_SYMBOL(memcg_kmem_enabled_key); struct workqueue_struct *memcg_kmem_cache_wq; +static int memcg_shrinker_map_size; +static DEFINE_MUTEX(memcg_shrinker_map_mutex); + +static void memcg_free_shrinker_map_rcu(struct rcu_head *head) +{ + kvfree(container_of(head, struct memcg_shrinker_map, rcu)); +} + +static int memcg_expand_one_shrinker_map(struct mem_cgroup *memcg, + int size, int old_size) +{ + struct memcg_shrinker_map *new, *old; + int nid; + + lockdep_assert_held(&memcg_shrinker_map_mutex); + + for_each_node(nid) { + old = rcu_dereference_protected( + mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true); + /* Not yet online memcg */ + if (!old) + return 0; + + new = kvmalloc(sizeof(*new) + size, GFP_KERNEL); + if (!new) + return -ENOMEM; + + /* Set all old bits, clear all new bits */ + memset(new->map, (int)0xff, old_size); + memset((void *)new->map + old_size, 0, size - old_size); + + rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new); + call_rcu(&old->rcu, memcg_free_shrinker_map_rcu); + } + + return 0; +} + +static void memcg_free_shrinker_maps(struct mem_cgroup *memcg) +{ + struct mem_cgroup_per_node *pn; + struct memcg_shrinker_map *map; + int nid; + + if (mem_cgroup_is_root(memcg)) + return; + + for_each_node(nid) { + pn = mem_cgroup_nodeinfo(memcg, nid); + map = rcu_dereference_protected(pn->shrinker_map, true); + if (map) + kvfree(map); + rcu_assign_pointer(pn->shrinker_map, NULL); + } +} + +static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg) +{ + struct memcg_shrinker_map *map; + int nid, size, ret = 0; + + if (mem_cgroup_is_root(memcg)) + return 0; + + mutex_lock(&memcg_shrinker_map_mutex); + size = memcg_shrinker_map_size; + for_each_node(nid) { + map = kvzalloc(sizeof(*map) + size, GFP_KERNEL); + if (!map) { + memcg_free_shrinker_maps(memcg); + ret = -ENOMEM; + break; + } + rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, map); + } + mutex_unlock(&memcg_shrinker_map_mutex); + + return ret; +} + +int memcg_expand_shrinker_maps(int new_id) +{ + int size, old_size, ret = 0; + struct mem_cgroup *memcg; + + size = DIV_ROUND_UP(new_id + 1, BITS_PER_LONG) * sizeof(unsigned long); + old_size = memcg_shrinker_map_size; + if (size <= old_size) + return 0; + + mutex_lock(&memcg_shrinker_map_mutex); + if (!root_mem_cgroup) + goto unlock; + + for_each_mem_cgroup(memcg) { + if (mem_cgroup_is_root(memcg)) + continue; + ret = memcg_expand_one_shrinker_map(memcg, size, old_size); + if (ret) + goto unlock; + } +unlock: + if (!ret) + memcg_shrinker_map_size = size; + mutex_unlock(&memcg_shrinker_map_mutex); + return ret; +} +#else /* CONFIG_MEMCG_KMEM */ +static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg) +{ + return 0; +} +static void memcg_free_shrinker_maps(struct mem_cgroup *memcg) { } #endif /* CONFIG_MEMCG_KMEM */ /** @@ -4356,6 +4469,16 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); + /* + * A memcg must be visible for memcg_expand_shrinker_maps() + * by the time the maps are allocated. So, we allocate maps + * here, when for_each_mem_cgroup() can't skip it. + */ + if (memcg_alloc_shrinker_maps(memcg)) { + mem_cgroup_id_remove(memcg); + return -ENOMEM; + } + /* Online state pins memcg ID, memcg ID pins CSS */ atomic_set(&memcg->id.ref, 1); css_get(css); @@ -4408,6 +4531,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css) vmpressure_cleanup(&memcg->vmpressure); cancel_work_sync(&memcg->high_work); mem_cgroup_remove_from_trees(memcg); + memcg_free_shrinker_maps(memcg); memcg_free_kmem(memcg); mem_cgroup_free(memcg); } -- cgit v1.2.3