linux-kernel - [PATCH] TIMER Refactoring: avoid unnecessary recalculation of cpu skew and remove duplication

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Date:   Sun, 26 Apr 2020 11:00:18 +0200
From:   Mátyás János <mjanos5@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        trivial@...nel.org
Subject: [PATCH] TIMER Refactoring: avoid unnecessary recalculation of cpu
 skew and remove duplication

commit 2a31a3b1db7898cf2360b628fa8717d85aac3e22
Author: Matyas Janos <mjanos5@...il.com>
Date:   Tue Oct 18 21:20:31 2016 +0200

Refactoring: avoid unnecessary recalculation of cpu skew and remove duplication

Signed-off-by: Matyas Janos <mjanos5@...il.com>
---
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index a5221abb4594..f6de4d68e652 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -275,6 +275,7 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu,
 {
 	int rem;
 	unsigned long original = j;
+	unsigned long cpu_skew = cpu * 3;
 
 	/*
 	 * We don't want all cpus firing their timers at once hitting the
@@ -284,7 +285,7 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu,
 	 * The skew is done by adding 3*cpunr, then round, then subtract this
 	 * extra offset again.
 	 */
-	j += cpu * 3;
+	j += cpu_skew;
 
 	rem = j % HZ;
 
@@ -295,13 +296,13 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu,
 	 * as cutoff for this rounding as an extreme upper bound for this.
 	 * But never round down if @force_up is set.
 	 */
-	if (rem < HZ/4 && !force_up) /* round down */
-		j = j - rem;
-	else /* round up */
-		j = j - rem + HZ;
+	j -= rem; /* round down by default */
+
+	if (rem >= HZ / 4 || force_up)
+		j += HZ; /* round up */
 
 	/* now that we have rounded, subtract the extra skew again */
-	j -= cpu * 3;
+	j -= cpu_skew;
 
 	/*
 	 * Make sure j is still in the future. Otherwise return the