vmscan: add customisable shrinker batch size

For shrinkers that have their own cond_resched* calls, having
shrink_slab break the work down into small batches is not
paticularly efficient. Add a custom batchsize field to the struct
shrinker so that shrinkers can use a larger batch size if they
desire.

A value of zero (uninitialised) means "use the default", so
behaviour is unchanged by this patch.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9670f71d7be9..9b9777ac726d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1150,6 +1150,7 @@ struct shrink_control {
 struct shrinker {
         int (*shrink)(struct shrinker *, struct shrink_control *sc);
         int seeks;      /* seeks to recreate an obj */
+        long batch;     /* reclaim batch size, 0 = default */
 
         /* These are for internal use */
         struct list_head list;