The patch titled
Subject: mm: add SHRINK_EMPTY shrinker methods return value
has been added to the -mm tree. Its filename is
mm-add-shrink_empty-shrinker-methods-return-value.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-shrink_empty-shrinker-methods-return-value.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-shrink_empty-shrinker-methods-return-value.patch
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------------------------------------------------------
From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Subject: mm: add SHRINK_EMPTY shrinker methods return value
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@xxxxxxxxxxxxx>
Acked-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Tested-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Josef Bacik <jbacik@xxxxxx>
Cc: Li RongQing <lirongqing@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/super.c | 3 +++
include/linux/shrinker.h | 7 +++++--
mm/vmscan.c | 12 +++++++++---
mm/workingset.c | 3 +++
4 files changed, 20 insertions(+), 5 deletions(-)
diff -puN fs/super.c~mm-add-shrink_empty-shrinker-methods-return-value fs/super.c
--- a/fs/super.c~mm-add-shrink_empty-shrinker-methods-return-value
+++ a/fs/super.c
@@ -144,6 +144,9 @@ static unsigned long super_cache_count(s
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 -puN include/linux/shrinker.h~mm-add-shrink_empty-shrinker-methods-return-value include/linux/shrinker.h
--- a/include/linux/shrinker.h~mm-add-shrink_empty-shrinker-methods-return-value
+++ a/include/linux/shrinker.h
@@ -34,12 +34,15 @@ 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 -puN mm/vmscan.c~mm-add-shrink_empty-shrinker-methods-return-value mm/vmscan.c
--- a/mm/vmscan.c~mm-add-shrink_empty-shrinker-methods-return-value
+++ a/mm/vmscan.c
@@ -453,8 +453,8 @@ static unsigned long do_shrink_slab(stru
long scanned = 0, next_deferred;
freeable = shrinker->count_objects(shrinker, shrinkctl);
- if (freeable == 0)
- return 0;
+ if (freeable == 0 || freeable == SHRINK_EMPTY)
+ return freeable;
/*
* copy the current shrinker scan count into a local variable
@@ -597,6 +597,8 @@ static unsigned long shrink_slab_memcg(g
continue;
ret = do_shrink_slab(&sc, shrinker, priority);
+ if (ret == SHRINK_EMPTY)
+ ret = 0;
freed += ret;
if (rwsem_is_contended(&shrinker_rwsem)) {
@@ -642,6 +644,7 @@ static unsigned long shrink_slab(gfp_t g
{
struct shrinker *shrinker;
unsigned long freed = 0;
+ int ret;
if (!mem_cgroup_is_root(memcg))
return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
@@ -659,7 +662,10 @@ static unsigned long shrink_slab(gfp_t g
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;
/*
* Bail out if someone want to register a new shrinker to
* prevent the regsitration from being stalled for long periods
diff -puN mm/workingset.c~mm-add-shrink_empty-shrinker-methods-return-value mm/workingset.c
--- a/mm/workingset.c~mm-add-shrink_empty-shrinker-methods-return-value
+++ a/mm/workingset.c
@@ -399,6 +399,9 @@ static unsigned long count_shadow_nodes(
}
max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
+ if (!nodes)
+ return SHRINK_EMPTY;
+
if (nodes <= max_nodes)
return 0;
return nodes - max_nodes;
_
Patches currently in -mm which might be from ktkhai@xxxxxxxxxxxxx are
memcg-remove-memcg_cgroup-id-from-idr-on-mem_cgroup_css_alloc-failure.patch
list_lru-combine-code-under-the-same-define.patch
mm-introduce-config_memcg_kmem-as-combination-of-config_memcg-config_slob.patch
mm-assign-id-to-every-memcg-aware-shrinker.patch
memcg-move-up-for_each_mem_cgroup-_tree-defines.patch
mm-assign-memcg-aware-shrinkers-bitmap-to-memcg.patch
mm-refactoring-in-workingset_init.patch
fs-refactoring-in-alloc_super.patch
fs-propagate-shrinker-id-to-list_lru.patch
list_lru-add-memcg-argument-to-list_lru_from_kmem.patch
list_lru-pass-dst_memcg-argument-to-memcg_drain_list_lru_node.patch
list_lru-pass-lru-argument-to-memcg_drain_list_lru_node.patch
mm-export-mem_cgroup_is_root.patch
mm-set-bit-in-memcg-shrinker-bitmap-on-first-list_lru-item-apearance.patch
mm-iterate-only-over-charged-shrinkers-during-memcg-shrink_slab.patch
mm-add-shrink_empty-shrinker-methods-return-value.patch
mm-clear-shrinker-bit-if-there-are-no-objects-related-to-memcg.patch
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