mm, slab: Drop unnecessary slabp->inuse < cachep->num test

PATCH In review Zhang Yanfei 2 participants 3 messages Jul 1, 2013 Memory management

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Zhang Yanfei

author

2013-07-01 16:30 UTC #0 lore raw

PATCH 1/1 mm, slab: Drop unnecessary slabp->inuse < cachep->num test

From: Zhang Yanfei <[email protected]>

In function cache_alloc_refill, we have used BUG_ON to ensure that slabp->inuse is less than cachep->num before the while test. And in the while body, we do not change the value of slabp->inuse and cachep->num, so it is not necessary to test if slabp->inuse < cachep->num test for every loop.

Signed-off-by Zhang Yanfei <[email protected]>

---
 mm/slab.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

mm/slab.c +1 -1

index 8ccd296..c2076c2 100644
@@ -3004,7 +3004,7 @@ retry:
 		 */
 		BUG_ON(slabp->inuse >= cachep->num);
 
-		while (slabp->inuse < cachep->num && batchcount--) {
+		while (batchcount--) {
 			STATS_INC_ALLOCED(cachep);
 			STATS_INC_ACTIVE(cachep);
 			STATS_SET_HIGH(cachep);

Signature · 7 lines

1.7.1

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Zhang Yanfei

author

2013-07-01 16:36 UTC #1 lore raw

Sorry for making noise. I've made a mistake and please ignore this patch.

Quoted 26 lines · Zhang Yanfei

From: Zhang Yanfei <[email protected]>
In function cache_alloc_refill, we have used BUG_ON to ensure that slabp->inuse is less than cachep->num before the while test. And in the while body, we do not change the value of slabp->inuse and cachep->num, so it is not necessary to test if slabp->inuse < cachep->num test for every loop.
Signed-off-by Zhang Yanfei <[email protected]>
---
 mm/slab.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
mm/slab.c +1 -1
index 8ccd296..c2076c2 100644
@@ -3004,7 +3004,7 @@ retry:
 		 */
 		BUG_ON(slabp->inuse >= cachep->num);
 
-		while (slabp->inuse < cachep->num && batchcount--) {
+		while (batchcount--) {
 			STATS_INC_ALLOCED(cachep);
 			STATS_INC_ACTIVE(cachep);
 			STATS_SET_HIGH(cachep);

Signature · 8 lines

Thanks.
Zhang Yanfei

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Christoph Lameter

2013-07-01 18:19 UTC #2 lore raw

In reply to Zhang Yanfei

Quoted 7 lines · Zhang Yanfei

From: Zhang Yanfei <[email protected]>
In function cache_alloc_refill, we have used BUG_ON to ensure that slabp->inuse is less than cachep->num before the while test. And in the while body, we do not change the value of slabp->inuse and cachep->num, so it is not necessary to test if slabp->inuse < cachep->num test for every loop.

The body calls slab_get_obj which changes slabp->inuse!

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