Messages in this thread Patch in this message |  | | From | Jiang Biao <> | Subject | [PATCH] mm/vmscan: try to optimize branch procedures. | Date | Tue, 28 Nov 2017 09:49:45 +0800 |
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1. Use unlikely to try to improve branch prediction. The *total_scan < 0* branch is unlikely to reach, so use unlikely.
2. Optimize *next_deferred >= scanned* condition. *next_deferred >= scanned* condition could be optimized into *next_deferred > scanned*, because when *next_deferred == scanned*, next_deferred shoud be 0, which is covered by the else branch.
3. Merge two branch blocks into one. The *next_deferred > 0* branch could be merged into *next_deferred > scanned* to simplify the code.
Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn> --- mm/vmscan.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index eb2f031..5f5d4ab 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -338,7 +338,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, delta *= freeable; do_div(delta, nr_eligible + 1); total_scan += delta; - if (total_scan < 0) { + if (unlikely(total_scan < 0)) { pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n", shrinker->scan_objects, total_scan); total_scan = freeable; @@ -407,18 +407,16 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, cond_resched(); } - if (next_deferred >= scanned) - next_deferred -= scanned; - else - next_deferred = 0; /* * move the unused scan count back into the shrinker in a * manner that handles concurrent updates. If we exhausted the * scan, there is no need to do an update. */ - if (next_deferred > 0) + if (next_deferred > scanned) { + next_deferred -= scanned; new_nr = atomic_long_add_return(next_deferred, &shrinker->nr_deferred[nid]); + } else new_nr = atomic_long_read(&shrinker->nr_deferred[nid]); -- 2.7.4
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