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Subject[PATCH 13/14] vfs: increase shrinker batch size
From: Dave Chinner <>

Now that the per-sb shrinker is responsible for shrinking 2 or more
caches, increase the batch size to keep econmies of scale for
shrinking each cache. Increase the shrinker batch size to 1024

To allow for a large increase in batch size, add a conditional
reschedule to prune_icache_sb() so that we don't hold the LRU spin
lock for too long. This mirrors the behaviour of the
__shrink_dcache_sb(), and allows us to increase the batch size
without needing to worry about problems caused by long lock hold

To ensure that filesystems using the per-sb shrinker callouts don't
cause problems, document that the object freeing method must
reschedule appropriately inside loops.

Signed-off-by: Dave Chinner <>
Documentation/filesystems/vfs.txt | 6 ++++++
fs/super.c | 1 +
2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index fd24f34..6bf85b7 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -317,6 +317,12 @@ or bottom half).
the VM is trying to reclaim under GFP_NOFS conditions, hence this
method does not need to handle that situation itself.

+ Implementations must include conditional reschedule calls inside any
+ scanning loop that is done. This allows the VFS to determine
+ appropriate scan batch sizes without having to worry about whether
+ implementations will cause holdoff problems due to large scan batch
+ sizes.
Whoever sets up the inode is responsible for filling in the "i_op" field. This
is a pointer to a "struct inode_operations" which describes the methods that
can be performed on individual inodes.
diff --git a/fs/super.c b/fs/super.c
index ca8e735..c1e0836 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -183,6 +183,7 @@ static struct super_block *alloc_super(struct file_system_type *type)

s->s_shrink.seeks = DEFAULT_SEEKS;
s->s_shrink.shrink = prune_super;
+ s->s_shrink.batch = 1024;
return s;

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