Use atomic-long operations instead of looping around cmpxchg().
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
---
include/linux/shrinker.h | 2 +-
mm/vmscan.c | 17 +++++++----------
2 files changed, 8 insertions(+), 11 deletions(-)
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 790651b..ac6b8ee 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -34,7 +34,7 @@ struct shrinker {
/* These are for internal use */
struct list_head list;
- long nr; /* objs pending delete */
+ atomic_long_t nr_in_batch; /* objs pending delete */
};
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
extern void register_shrinker(struct shrinker *);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f174561..e31c3e2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -184,7 +184,7 @@ static unsigned long zone_nr_lru_pages(struct zone *zone,
*/
void register_shrinker(struct shrinker *shrinker)
{
- shrinker->nr = 0;
+ atomic_long_set(&shrinker->nr_in_batch, 0);
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
up_write(&shrinker_rwsem);
@@ -265,9 +265,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
* and zero it so that other concurrent shrinker invocations
* don't also do this scanning work.
*/
- do {
- nr = shrinker->nr;
- } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
+ nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
total_scan = nr;
delta = (4 * nr_pages_scanned) / shrinker->seeks;
@@ -329,12 +327,11 @@ unsigned long shrink_slab(struct shrink_control *shrink,
* manner that handles concurrent updates. If we exhausted the
* scan, there is no need to do an update.
*/
- do {
- nr = shrinker->nr;
- new_nr = total_scan + nr;
- if (total_scan <= 0)
- break;
- } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
+ if (total_scan > 0)
+ new_nr = atomic_long_add_return(total_scan,
+ &shrinker->nr_in_batch);
+ else
+ new_nr = atomic_long_read(&shrinker->nr_in_batch);
trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
}
--
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