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/gfs2/quota.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs/gfs2') diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c index 3e193cb..c15d6b2 100644 --- a/fs/gfs2/quota.c +++ b/fs/gfs2/quota.c @@ -171,8 +171,8 @@ static unsigned long gfs2_qd_shrink_scan(struct shrinker *shrink, if (!(sc->gfp_mask & __GFP_FS)) return SHRINK_STOP; - freed = list_lru_walk_node(&gfs2_qd_lru, sc->nid, gfs2_qd_isolate, - &dispose, &sc->nr_to_scan); + freed = list_lru_shrink_walk(&gfs2_qd_lru, sc, + gfs2_qd_isolate, &dispose); gfs2_qd_dispose(&dispose); @@ -182,7 +182,7 @@ static unsigned long gfs2_qd_shrink_scan(struct shrinker *shrink, static unsigned long gfs2_qd_shrink_count(struct shrinker *shrink, struct shrink_control *sc) { - return vfs_pressure_ratio(list_lru_count_node(&gfs2_qd_lru, sc->nid)); + return vfs_pressure_ratio(list_lru_shrink_count(&gfs2_qd_lru, sc)); } struct shrinker gfs2_qd_shrinker = { -- cgit v1.1 From 3f97b163207c67a3b35931494ad3db1de66356f0 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Thu, 12 Feb 2015 14:59:35 -0800 Subject: list_lru: add helpers to isolate items Currently, the isolate callback passed to the list_lru_walk family of functions is supposed to just delete an item from the list upon returning LRU_REMOVED or LRU_REMOVED_RETRY, while nr_items counter is fixed by __list_lru_walk_one after the callback returns. Since the callback is allowed to drop the lock after removing an item (it has to return LRU_REMOVED_RETRY then), the nr_items can be less than the actual number of elements on the list even if we check them under the lock. This makes it difficult to move items from one list_lru_one to another, which is required for per-memcg list_lru reparenting - we can't just splice the lists, we have to move entries one by one. This patch therefore introduces helpers that must be used by callback functions to isolate items instead of raw list_del/list_move. These are list_lru_isolate and list_lru_isolate_move. They not only remove the entry from the list, but also fix the nr_items counter, making sure nr_items always reflects the actual number of elements on the list if checked under the appropriate lock. Signed-off-by: Vladimir Davydov Cc: Johannes Weiner Cc: Michal Hocko Cc: Tejun Heo Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/gfs2/quota.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'fs/gfs2') diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c index c15d6b2..3aa17d4 100644 --- a/fs/gfs2/quota.c +++ b/fs/gfs2/quota.c @@ -145,7 +145,8 @@ static void gfs2_qd_dispose(struct list_head *list) } -static enum lru_status gfs2_qd_isolate(struct list_head *item, spinlock_t *lock, void *arg) +static enum lru_status gfs2_qd_isolate(struct list_head *item, + struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) { struct list_head *dispose = arg; struct gfs2_quota_data *qd = list_entry(item, struct gfs2_quota_data, qd_lru); @@ -155,7 +156,7 @@ static enum lru_status gfs2_qd_isolate(struct list_head *item, spinlock_t *lock, if (qd->qd_lockref.count == 0) { lockref_mark_dead(&qd->qd_lockref); - list_move(&qd->qd_lru, dispose); + list_lru_isolate_move(lru, &qd->qd_lru, dispose); } spin_unlock(&qd->qd_lockref.lock); -- cgit v1.1