From: Andrew Morton <akpm@linux-foundation.org>
Date: Thu, 14 Dec 2017 23:32:31 +0000 (-0800)
Subject: mm/kmemleak.c: make cond_resched() rate-limiting more efficient
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=13ab183d138f607d885e995d625e58d47678bf97;p=openwrt%2Fstaging%2Fblogic.git

mm/kmemleak.c: make cond_resched() rate-limiting more efficient

Commit bde5f6bc68db ("kmemleak: add scheduling point to
kmemleak_scan()") tries to rate-limit the frequency of cond_resched()
calls, but does it in a way which might incur an expensive division
operation in the inner loop.  Simplify this.

Fixes: bde5f6bc68db5 ("kmemleak: add scheduling point to kmemleak_scan()")
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 3d4781756d50..d73c14294f3a 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1523,7 +1523,7 @@ static void kmemleak_scan(void)
 			if (page_count(page) == 0)
 				continue;
 			scan_block(page, page + 1, NULL);
-			if (!(pfn % (MAX_SCAN_SIZE / sizeof(*page))))
+			if (!(pfn & 63))
 				cond_resched();
 		}
 	}