[RHEL7,COMMIT] ms/mm: add SHRINK_EMPTY shrinker methods return value

Submitted by Konstantin Khorenko on Sept. 5, 2018, 9:37 a.m.

Details

Message ID 201809050937.w859bFn6010499@finist_ce7.work
State New
Series "Port "Improve shrink_slab() scalability" patchset"
Headers show

Commit Message

Konstantin Khorenko Sept. 5, 2018, 9:37 a.m.
The commit is pushed to "branch-rh7-3.10.0-862.11.6.vz7.71.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-862.11.6.vz7.71.8
------>
commit 20206759adaacb5166e5474ebc959f6961700c4f
Author: Kirill Tkhai <ktkhai@virtuozzo.com>
Date:   Wed Sep 5 12:37:15 2018 +0300

    ms/mm: add SHRINK_EMPTY shrinker methods return value
    
    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 <ktkhai@virtuozzo.com>
    
    Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
    Tested-by: Shakeel Butt <shakeelb@google.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
    Cc: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Guenter Roeck <linux@roeck-us.net>
    Cc: "Huang, Ying" <ying.huang@intel.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Josef Bacik <jbacik@fb.com>
    Cc: Li RongQing <lirongqing@baidu.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Matthias Kaehlcke <mka@chromium.org>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Philippe Ombredanne <pombredanne@nexb.com>
    Cc: Roman Gushchin <guro@fb.com>
    Cc: Sahitya Tummala <stummala@codeaurora.org>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Waiman Long <longman@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
    
    =====================
    Patchset description:
    
    Port "Improve shrink_slab() scalability" patchset
    
    https://jira.sw.ru/browse/PSBM-88027
    
    This is backport of the patchset improving the performance
    of overcommited containers with many memcgs and mounts.
    The original set is in Linus' tree, and came into 4.19-rc1.
    
    Kirill Tkhai (12):
          mm: assign id to every memcg-aware shrinker
          mm/memcontrol.c: move up for_each_mem_cgroup{, _tree} defines
          mm, memcg: assign memcg-aware shrinkers bitmap to memcg
          fs: propagate shrinker::id to list_lru
          mm/list_lru.c: add memcg argument to list_lru_from_kmem()
          mm/list_lru: pass dst_memcg argument to memcg_drain_list_lru_node()
          mm/list_lru.c: pass lru argument to memcg_drain_list_lru_node()
          mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance
          mm/memcontrol.c: export mem_cgroup_is_root()
          mm/vmscan.c: iterate only over charged shrinkers during memcg shrink_slab()
          mm: add SHRINK_EMPTY shrinker methods return value
          mm/vmscan.c: clear shrinker bit if there are no objects related to memcg
    
    Vladimir Davydov (1):
          mm/vmscan.c: generalize shrink_slab() calls in shrink_node()
---
 fs/super.c               |  3 +++
 include/linux/shrinker.h |  7 +++++--
 mm/vmscan.c              | 12 +++++++++---
 3 files changed, 17 insertions(+), 5 deletions(-)

Patch hide | download patch | download mbox

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);