ms commit 9b996468cfdb We need to distinguish the situations when shrinker has very small amount of objects (see vfs_pressure_ratio() called from super_cache_count()), and when it has no objects at all. Currently, in the both of these cases, shrinker::count_objects() returns 0.
The patch introduces new SHRINK_EMPTY return value, which will be used for "no objects at all" case. It's is a refactoring mostly, as SHRINK_EMPTY is replaced by 0 by all callers of do_shrink_slab() in this patch, and all the magic will happen in further. Link: http://lkml.kernel.org/r/153063069574.1818.11037751256699341813.stgit@localhost.localdomain Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com> Acked-by: Vladimir Davydov <vdavydov....@gmail.com> Tested-by: Shakeel Butt <shake...@google.com> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: Andrey Ryabinin <aryabi...@virtuozzo.com> Cc: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Guenter Roeck <li...@roeck-us.net> Cc: "Huang, Ying" <ying.hu...@intel.com> Cc: Johannes Weiner <han...@cmpxchg.org> Cc: Josef Bacik <jba...@fb.com> Cc: Li RongQing <lirongq...@baidu.com> Cc: Matthew Wilcox <wi...@infradead.org> Cc: Matthias Kaehlcke <m...@chromium.org> Cc: Mel Gorman <mgor...@techsingularity.net> Cc: Michal Hocko <mho...@kernel.org> Cc: Minchan Kim <minc...@kernel.org> Cc: Philippe Ombredanne <pombreda...@nexb.com> Cc: Roman Gushchin <g...@fb.com> Cc: Sahitya Tummala <stumm...@codeaurora.org> Cc: Stephen Rothwell <s...@canb.auug.org.au> Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Waiman Long <long...@redhat.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com> --- fs/super.c | 3 +++ include/linux/shrinker.h | 7 +++++-- mm/vmscan.c | 12 +++++++++--- 3 files changed, 17 insertions(+), 5 deletions(-) diff --git a/fs/super.c b/fs/super.c index 162ca145940f..f825c142bf97 100644 --- a/fs/super.c +++ b/fs/super.c @@ -156,6 +156,9 @@ static unsigned long super_cache_count(struct shrinker *shrink, total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); + if (!total_objects) + return SHRINK_EMPTY; + total_objects = vfs_pressure_ratio(total_objects); return total_objects; } diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index a8bbeaa3c66e..f6938dc6c068 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -28,12 +28,15 @@ struct shrink_control { }; #define SHRINK_STOP (~0UL) +#define SHRINK_EMPTY (~0UL - 1) /* * A callback you can register to apply pressure to ageable caches. * * @count_objects should return the number of freeable items in the cache. If - * there are no objects to free or the number of freeable items cannot be - * determined, it should return 0. No deadlock checks should be done during the + * there are no objects to free, it should return SHRINK_EMPTY, while 0 is + * returned in cases of the number of freeable items cannot be determined + * or shrinker should skip this cache for this time (e.g., their number + * is below shrinkable limit). No deadlock checks should be done during the * count callback - the shrinker relies on aggregating scan counts that couldn't * be executed due to potential deadlocks to be run at a later call when the * deadlock condition is no longer pending. diff --git a/mm/vmscan.c b/mm/vmscan.c index bd2d62dabdd9..da28fc98f0a0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -350,8 +350,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, : SHRINK_BATCH; max_pass = shrinker->count_objects(shrinker, shrinkctl); - if (max_pass == 0) - return 0; + if (max_pass == 0 || max_pass == SHRINK_EMPTY) + return max_pass; /* * copy the current shrinker scan count into a local variable @@ -464,6 +464,8 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, } ret = do_shrink_slab(&sc, shrinker, priority); + if (ret == SHRINK_EMPTY) + ret = 0; freed += ret; if (rwsem_is_contended(&shrinker_rwsem)) { @@ -513,6 +515,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, { struct shrinker *shrinker; unsigned long freed = 0; + int ret; if (unlikely(test_tsk_thread_flag(current, TIF_MEMDIE))) return 0; @@ -542,7 +545,10 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) sc.nid = 0; - freed += do_shrink_slab(&sc, shrinker, priority); + ret = do_shrink_slab(&sc, shrinker, priority); + if (ret == SHRINK_EMPTY) + ret = 0; + freed += ret; } up_read(&shrinker_rwsem); _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
