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authorQi Zheng <zhengqi.arch@bytedance.com>2023-06-09 08:15:12 +0000
committerAndrew Morton <akpm@linux-foundation.org>2023-06-19 13:19:33 -0700
commit47a7c01c3efc6581f5dcca40928baeb38e1e40c2 (patch)
tree00073c63c91b68b1fb45cb3cdbeb9aee5c396945 /mm/shrinker_debug.c
parent679bd7ebdd315bf457a4740b306ae99f1d0a403d (diff)
Revert "mm: shrinkers: convert shrinker_rwsem to mutex"
Patch series "revert shrinker_srcu related changes". This patch (of 7): This reverts commit cf2e309ebca7bb0916771839f9b580b06c778530. Kernel test robot reports -88.8% regression in stress-ng.ramfs.ops_per_sec test case [1], which is caused by commit f95bdb700bc6 ("mm: vmscan: make global slab shrink lockless"). The root cause is that SRCU has to be careful to not frequently check for SRCU read-side critical section exits. Therefore, even if no one is currently in the SRCU read-side critical section, synchronize_srcu() cannot return quickly. That's why unregister_shrinker() has become slower. After discussion, we will try to use the refcount+RCU method [2] proposed by Dave Chinner to continue to re-implement the lockless slab shrink. So revert the shrinker_mutex back to shrinker_rwsem first. [1]. https://lore.kernel.org/lkml/202305230837.db2c233f-yujie.liu@intel.com/ [2]. https://lore.kernel.org/lkml/ZIJhou1d55d4H1s0@dread.disaster.area/ Link: https://lkml.kernel.org/r/20230609081518.3039120-1-qi.zheng@linux.dev Link: https://lkml.kernel.org/r/20230609081518.3039120-2-qi.zheng@linux.dev Reported-by: kernel test robot <yujie.liu@intel.com> Closes: https://lore.kernel.org/oe-lkp/202305230837.db2c233f-yujie.liu@intel.com Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Kirill Tkhai <tkhai@ya.ru> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yujie Liu <yujie.liu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/shrinker_debug.c')
-rw-r--r--mm/shrinker_debug.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index fe10436d9911..2be15b8a6d0b 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -8,7 +8,7 @@
#include <linux/srcu.h>
/* defined in vmscan.c */
-extern struct mutex shrinker_mutex;
+extern struct rw_semaphore shrinker_rwsem;
extern struct list_head shrinker_list;
extern struct srcu_struct shrinker_srcu;
@@ -168,7 +168,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
char buf[128];
int id;
- lockdep_assert_held(&shrinker_mutex);
+ lockdep_assert_held(&shrinker_rwsem);
/* debugfs isn't initialized yet, add debugfs entries later. */
if (!shrinker_debugfs_root)
@@ -211,7 +211,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
if (!new)
return -ENOMEM;
- mutex_lock(&shrinker_mutex);
+ down_write(&shrinker_rwsem);
old = shrinker->name;
shrinker->name = new;
@@ -229,7 +229,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
shrinker->debugfs_entry = entry;
}
- mutex_unlock(&shrinker_mutex);
+ up_write(&shrinker_rwsem);
kfree_const(old);
@@ -242,7 +242,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
{
struct dentry *entry = shrinker->debugfs_entry;
- lockdep_assert_held(&shrinker_mutex);
+ lockdep_assert_held(&shrinker_rwsem);
kfree_const(shrinker->name);
shrinker->name = NULL;
@@ -271,14 +271,14 @@ static int __init shrinker_debugfs_init(void)
shrinker_debugfs_root = dentry;
/* Create debugfs entries for shrinkers registered at boot */
- mutex_lock(&shrinker_mutex);
+ down_write(&shrinker_rwsem);
list_for_each_entry(shrinker, &shrinker_list, list)
if (!shrinker->debugfs_entry) {
ret = shrinker_debugfs_add(shrinker);
if (ret)
break;
}
- mutex_unlock(&shrinker_mutex);
+ up_write(&shrinker_rwsem);
return ret;
}