From 55f841ce9395a72c6285fbcc4c403c0c786e1c74 Mon Sep 17 00:00:00 2001 From: Glauber Costa Date: Wed, 28 Aug 2013 10:17:53 +1000 Subject: super: fix calculation of shrinkable objects for small numbers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The sysctl knob sysctl_vfs_cache_pressure is used to determine which percentage of the shrinkable objects in our cache we should actively try to shrink. It works great in situations in which we have many objects (at least more than 100), because the aproximation errors will be negligible. But if this is not the case, specially when total_objects < 100, we may end up concluding that we have no objects at all (total / 100 = 0, if total < 100). This is certainly not the biggest killer in the world, but may matter in very low kernel memory situations. Signed-off-by: Glauber Costa Reviewed-by: Carlos Maiolino Acked-by: KAMEZAWA Hiroyuki Acked-by: Mel Gorman Cc: Dave Chinner Cc: Al Viro Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/mbcache.c') diff --git a/fs/mbcache.c b/fs/mbcache.c index 8c32ef3ba88e..5eb04767cb29 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -189,7 +189,7 @@ mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc) list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { __mb_cache_entry_forget(entry, gfp_mask); } - return (count / 100) * sysctl_vfs_cache_pressure; + return vfs_pressure_ratio(count); } -- cgit v1.2.3 From 1ab6c4997e04a00c50c6d786c2f046adc0d1f5de Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 28 Aug 2013 10:18:09 +1000 Subject: fs: convert fs shrinkers to new scan/count API MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Convert the filesystem shrinkers to use the new API, and standardise some of the behaviours of the shrinkers at the same time. For example, nr_to_scan means the number of objects to scan, not the number of objects to free. I refactored the CIFS idmap shrinker a little - it really needs to be broken up into a shrinker per tree and keep an item count with the tree root so that we don't need to walk the tree every time the shrinker needs to count the number of objects in the tree (i.e. all the time under memory pressure). [glommer@openvz.org: fixes for ext4, ubifs, nfs, cifs and glock. Fixes are needed mainly due to new code merged in the tree] [assorted fixes folded in] Signed-off-by: Dave Chinner Signed-off-by: Glauber Costa Acked-by: Mel Gorman Acked-by: Artem Bityutskiy Acked-by: Jan Kara Acked-by: Steven Whitehouse Cc: Adrian Hunter Cc: "Theodore Ts'o" Cc: Adrian Hunter Cc: Al Viro Cc: Artem Bityutskiy Cc: Arve Hjønnevåg Cc: Carlos Maiolino Cc: Christoph Hellwig Cc: Chuck Lever Cc: Daniel Vetter Cc: David Rientjes Cc: Gleb Natapov Cc: Greg Thelen Cc: J. Bruce Fields Cc: Jan Kara Cc: Jerome Glisse Cc: John Stultz Cc: KAMEZAWA Hiroyuki Cc: Kent Overstreet Cc: Kirill A. Shutemov Cc: Marcelo Tosatti Cc: Mel Gorman Cc: Steven Whitehouse Cc: Thomas Hellstrom Cc: Trond Myklebust Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/mbcache.c | 47 ++++++++++++++++++++++++++--------------------- 1 file changed, 26 insertions(+), 21 deletions(-) (limited to 'fs/mbcache.c') diff --git a/fs/mbcache.c b/fs/mbcache.c index 5eb04767cb29..e519e45bf673 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -86,18 +86,6 @@ static LIST_HEAD(mb_cache_list); static LIST_HEAD(mb_cache_lru_list); static DEFINE_SPINLOCK(mb_cache_spinlock); -/* - * What the mbcache registers as to get shrunk dynamically. - */ - -static int mb_cache_shrink_fn(struct shrinker *shrink, - struct shrink_control *sc); - -static struct shrinker mb_cache_shrinker = { - .shrink = mb_cache_shrink_fn, - .seeks = DEFAULT_SEEKS, -}; - static inline int __mb_cache_entry_is_hashed(struct mb_cache_entry *ce) { @@ -151,7 +139,7 @@ forget: /* - * mb_cache_shrink_fn() memory pressure callback + * mb_cache_shrink_scan() memory pressure callback * * This function is called by the kernel memory management when memory * gets low. @@ -159,17 +147,16 @@ forget: * @shrink: (ignored) * @sc: shrink_control passed from reclaim * - * Returns the number of objects which are present in the cache. + * Returns the number of objects freed. */ -static int -mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc) +static unsigned long +mb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { LIST_HEAD(free_list); - struct mb_cache *cache; struct mb_cache_entry *entry, *tmp; - int count = 0; int nr_to_scan = sc->nr_to_scan; gfp_t gfp_mask = sc->gfp_mask; + unsigned long freed = 0; mb_debug("trying to free %d entries", nr_to_scan); spin_lock(&mb_cache_spinlock); @@ -179,19 +166,37 @@ mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc) struct mb_cache_entry, e_lru_list); list_move_tail(&ce->e_lru_list, &free_list); __mb_cache_entry_unhash(ce); + freed++; + } + spin_unlock(&mb_cache_spinlock); + list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { + __mb_cache_entry_forget(entry, gfp_mask); } + return freed; +} + +static unsigned long +mb_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc) +{ + struct mb_cache *cache; + unsigned long count = 0; + + spin_lock(&mb_cache_spinlock); list_for_each_entry(cache, &mb_cache_list, c_cache_list) { mb_debug("cache %s (%d)", cache->c_name, atomic_read(&cache->c_entry_count)); count += atomic_read(&cache->c_entry_count); } spin_unlock(&mb_cache_spinlock); - list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { - __mb_cache_entry_forget(entry, gfp_mask); - } + return vfs_pressure_ratio(count); } +static struct shrinker mb_cache_shrinker = { + .count_objects = mb_cache_shrink_count, + .scan_objects = mb_cache_shrink_scan, + .seeks = DEFAULT_SEEKS, +}; /* * mb_cache_create() create a new cache -- cgit v1.2.3