From 503c358cf1925853195ee39ec437e51138bbb7df Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 12 Feb 2015 14:58:47 -0800 Subject: list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov Suggested-by: Dave Chinner Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Glauber Costa Cc: Alexander Viro Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/super.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) (limited to 'fs/super.c') diff --git a/fs/super.c b/fs/super.c index eae088f6aaae..4554ac257647 100644 --- a/fs/super.c +++ b/fs/super.c @@ -77,8 +77,8 @@ static unsigned long super_cache_scan(struct shrinker *shrink, if (sb->s_op->nr_cached_objects) fs_objects = sb->s_op->nr_cached_objects(sb, sc->nid); - inodes = list_lru_count_node(&sb->s_inode_lru, sc->nid); - dentries = list_lru_count_node(&sb->s_dentry_lru, sc->nid); + inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); + dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc); total_objects = dentries + inodes + fs_objects + 1; if (!total_objects) total_objects = 1; @@ -86,20 +86,20 @@ static unsigned long super_cache_scan(struct shrinker *shrink, /* proportion the scan between the caches */ dentries = mult_frac(sc->nr_to_scan, dentries, total_objects); inodes = mult_frac(sc->nr_to_scan, inodes, total_objects); + fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects); /* * prune the dcache first as the icache is pinned by it, then * prune the icache, followed by the filesystem specific caches */ - freed = prune_dcache_sb(sb, dentries, sc->nid); - freed += prune_icache_sb(sb, inodes, sc->nid); + sc->nr_to_scan = dentries; + freed = prune_dcache_sb(sb, sc); + sc->nr_to_scan = inodes; + freed += prune_icache_sb(sb, sc); - if (fs_objects) { - fs_objects = mult_frac(sc->nr_to_scan, fs_objects, - total_objects); + if (fs_objects) freed += sb->s_op->free_cached_objects(sb, fs_objects, sc->nid); - } drop_super(sb); return freed; @@ -118,17 +118,15 @@ static unsigned long super_cache_count(struct shrinker *shrink, * scalability bottleneck. The counts could get updated * between super_cache_count and super_cache_scan anyway. * Call to super_cache_count with shrinker_rwsem held - * ensures the safety of call to list_lru_count_node() and + * ensures the safety of call to list_lru_shrink_count() and * s_op->nr_cached_objects(). */ if (sb->s_op && sb->s_op->nr_cached_objects) total_objects = sb->s_op->nr_cached_objects(sb, sc->nid); - total_objects += list_lru_count_node(&sb->s_dentry_lru, - sc->nid); - total_objects += list_lru_count_node(&sb->s_inode_lru, - sc->nid); + total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); + total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); total_objects = vfs_pressure_ratio(total_objects); return total_objects; -- cgit v1.2.3