linux-kernel - [PATCH] mm: Place "not" inside of unlikely() statement in wb_domain_writeout

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Message-ID: <20170206120035.3c2e2b91@gandalf.local.home>
Date:   Mon, 6 Feb 2017 12:00:35 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>
Subject: [PATCH] mm: Place "not" inside of unlikely() statement in
 wb_domain_writeout_inc()

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

The likely/unlikely profiler noticed that the unlikely statement in
wb_domain_writeout_inc() is constantly wrong. This is due to the "not" (!)
being outside the unlikely statement. It is likely that dom->period_time
will be set, but unlikely that it wont be. Move the not into the unlikely
statement.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 mm/page-writeback.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 290e8b7..94102c7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -580,7 +580,7 @@ static void wb_domain_writeout_inc(struct wb_domain *dom,
 	__fprop_inc_percpu_max(&dom->completions, completions,
 			       max_prop_frac);
 	/* First event after period switching was turned off? */
-	if (!unlikely(dom->period_time)) {
+	if (unlikely(!dom->period_time)) {
 		/*
 		 * We can race with other __bdi_writeout_inc calls here but
 		 * it does not cause any harm since the resulting time when
-- 
2.9.3