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 --- include/linux/list_lru.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux/list_lru.h') diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h index f3434533fbf8..f500a2e39b13 100644 --- a/include/linux/list_lru.h +++ b/include/linux/list_lru.h @@ -9,6 +9,7 @@ #include #include +#include /* list_lru_walk_cb has to always return one of those */ enum lru_status { @@ -81,6 +82,13 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item); * Callers that want such a guarantee need to provide an outer lock. */ unsigned long list_lru_count_node(struct list_lru *lru, int nid); + +static inline unsigned long list_lru_shrink_count(struct list_lru *lru, + struct shrink_control *sc) +{ + return list_lru_count_node(lru, sc->nid); +} + static inline unsigned long list_lru_count(struct list_lru *lru) { long count = 0; @@ -119,6 +127,14 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid, list_lru_walk_cb isolate, void *cb_arg, unsigned long *nr_to_walk); +static inline unsigned long +list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc, + list_lru_walk_cb isolate, void *cb_arg) +{ + return list_lru_walk_node(lru, sc->nid, isolate, cb_arg, + &sc->nr_to_scan); +} + static inline unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate, void *cb_arg, unsigned long nr_to_walk) -- cgit