linux-kernel - [PATCH] sched: reorder root_domain to remove 64 bit alignment padding

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Date:	Fri, 15 Jul 2011 11:41:31 +0100
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH] sched: reorder root_domain to remove 64 bit alignment
 padding

Reorder root_domain to remove 8 bytes of alignment padding on 64 bit
builds, this shrinks the size from 1736 to 1728 bytes, therefore using
one fewer cachelines.

Signed-off-by: Richard Kennedy <richard@....demon.co.uk>
---

patch against v3.0-rc7

compiled & booted on x86_64.

I've been running this patch for 2 days without any obvious problems,
but I don't have any specific RT test cases.

regards
Richard



diff --git a/kernel/sched.c b/kernel/sched.c
index 9769c75..4ecf9db 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -422,6 +422,7 @@ struct rt_rq {
  */
 struct root_domain {
 	atomic_t refcount;
+	atomic_t rto_count;
 	struct rcu_head rcu;
 	cpumask_var_t span;
 	cpumask_var_t online;
@@ -431,7 +432,6 @@ struct root_domain {
 	 * one runnable RT task.
 	 */
 	cpumask_var_t rto_mask;
-	atomic_t rto_count;
 	struct cpupri cpupri;
 };
 


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