linux-kernel - [PATCH] trace: reorder perf_event_context to remove alignment padding on 64 bit builds

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Message-ID: <1299512819.2039.5.camel@castor.rsk>
Date:	Mon, 07 Mar 2011 15:46:59 +0000
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Paul Mackerras <paulus@...ba.org>
Subject: [PATCH] trace: reorder perf_event_context to remove alignment
 padding on 64 bit builds

Remove 8 bytes of alignment padding from perf_event_context on 64 bit
builds which shrinks its size to 192 bytes allowing it to fit into one
fewer cache lines and into a smaller slab.

Signed-off-by: Richard Kennedy <richard@....demon.co.uk>
---
patch against v2.6.38-rc7
compiled and tested on x86_64

regards
Richard



diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index dda5b0a..59792fe 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -846,8 +846,8 @@ enum perf_event_context_type {
  * Used as a container for task events and CPU events as well:
  */
 struct perf_event_context {
-	enum perf_event_context_type	type;
 	struct pmu			*pmu;
+	enum perf_event_context_type	type;
 	/*
 	 * Protect the states of the events in the list,
 	 * nr_active, and the list:


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