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>

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>
Dave Chinner · Al Viro
1 parent 3567b59aa8
Showing 2 changed files with 7 additions and 5 deletions Side-by-side Diff
include/linux/mm.h
mm/vmscan.c
@@ -1150,6 +1150,7 @@
 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;
@@ -253,6 +253,8 @@
 		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
  
  
@@ -303,19 +305,18 @@
 					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();
 		}
...	...	@@ -1150,6 +1150,7 @@
1150	1150	struct shrinker {
1151	1151	int (shrink)(struct shrinker , struct shrink_control *sc);
1152	1152	int seeks; /* seeks to recreate an obj */
	1153	+ long batch; /* reclaim batch size, 0 = default */
1153	1154
1154	1155	/* These are for internal use */
1155	1156	struct list_head list;
...	...	@@ -253,6 +253,8 @@
253	253	int shrink_ret = 0;
254	254	long nr;
255	255	long new_nr;
	256	+ long batch_size = shrinker->batch ? shrinker->batch
	257	+ : SHRINK_BATCH;
256	258
257	259	/*
258	260	* copy the current shrinker scan count into a local variable
259	261
260	262
...	...	@@ -303,19 +305,18 @@
303	305	nr_pages_scanned, lru_pages,
304	306	max_pass, delta, total_scan);
305	307
306		- while (total_scan >= SHRINK_BATCH) {
307		- long this_scan = SHRINK_BATCH;
	308	+ while (total_scan >= batch_size) {
308	309	int nr_before;
309	310
310	311	nr_before = do_shrinker_shrink(shrinker, shrink, 0);
311	312	shrink_ret = do_shrinker_shrink(shrinker, shrink,
312		- this_scan);
	313	+ batch_size);
313	314	if (shrink_ret == -1)
314	315	break;
315	316	if (shrink_ret < nr_before)
316	317	ret += nr_before - shrink_ret;
317		- count_vm_events(SLABS_SCANNED, this_scan);
318		- total_scan -= this_scan;
	318	+ count_vm_events(SLABS_SCANNED, batch_size);
	319	+ total_scan -= batch_size;
319	320
320	321	cond_resched();
321	322	}