[PATCH 04/12] vmscan: add customisable shrinker batch size

Dave Chinner
2011-06-02T07:01:51Z

From: Dave Chinner <dchinner@redhat.com>

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>
---
include/linux/mm.h | 1 +
mm/vmscan.c | 11 ++++++-----
2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9670f71..9b9777a 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;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3688f47..a17909f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -253,6 +253,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
int shrink_ret = 0;
long nr;
long new_nr;
+ long batch_size = shrinker->batch ? shrinker->batch
+ : SHRINK_BATCH;

/*
* copy the current shrinker scan count into a local variable
@@ -302,19 +304,18 @@ unsigned long shrink_slab(struct shrink_control *shrink,
trace_mm_shrink_slab_start(shrinker, shrink, nr, nr_pages_scanned,
lru_pages, max_pass, delta, total_scan);

- while (total_scan >= SHRINK_BATCH) {
- long this_scan = SHRINK_BATCH;
+ while (total_scan >= batch_size) {
int nr_before;

nr_before = do_shrinker_shrink(shrinker, shrink, 0);
shrink_ret = do_shrinker_shrink(shrinker, shrink,
- this_scan);
+ batch_size);
if (shrink_ret == -1)
break;
if (shrink_ret < nr_before)
ret += nr_before - shrink_ret;
- count_vm_events(SLABS_SCANNED, this_scan);
- total_scan -= this_scan;
+ count_vm_events(SLABS_SCANNED, batch_size);
+ total_scan -= batch_size;

cond_resched();
}
--
1.7.5.1