linux-kernel - [PATCH] mm/page_alloc.c: micro-optimization remove unnecessary branch

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Date:   Fri, 11 Sep 2020 11:23:10 +0200
From:   mateusznosek0@...il.com
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Mateusz Nosek <mateusznosek0@...il.com>, akpm@...ux-foundation.org
Subject: [PATCH] mm/page_alloc.c: micro-optimization remove unnecessary branch

From: Mateusz Nosek <mateusznosek0@...il.com>

Previously flags check was separated into two separated checks with two
separated branches. In case of presence of any of two mentioned flags,
the same effect on flow occurs. Therefore checks can be merged and one
branch can be avoided.

Signed-off-by: Mateusz Nosek <mateusznosek0@...il.com>
---
 mm/page_alloc.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cefbef32bf4a..b9bd75cacf02 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3972,8 +3972,10 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 	 * success so it is time to admit defeat. We will skip the OOM killer
 	 * because it is very likely that the caller has a more reasonable
 	 * fallback than shooting a random task.
+	 *
+	 * The OOM killer may not free memory on a specific node.
 	 */
-	if (gfp_mask & __GFP_RETRY_MAYFAIL)
+	if (gfp_mask & (__GFP_RETRY_MAYFAIL | __GFP_THISNODE))
 		goto out;
 	/* The OOM killer does not needlessly kill tasks for lowmem */
 	if (ac->highest_zoneidx < ZONE_NORMAL)
@@ -3990,10 +3992,6 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 	 * failures more gracefully we should just bail out here.
 	 */
 
-	/* The OOM killer may not free memory on a specific node */
-	if (gfp_mask & __GFP_THISNODE)
-		goto out;
-
 	/* Exhausted what can be done so it's blame time */
 	if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
 		*did_some_progress = 1;
-- 
2.20.1