linux-kernel - [PATCH] timer_list: remove alignment padding on 64 bit when CONFIG_TIMER

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Date:	Mon, 26 Jul 2010 09:54:52 +0100
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH] timer_list: remove alignment padding on 64 bit when
 CONFIG_TIMER_STATS

Re-order structure timer_list to remove 8 bytes of alignment padding on
64 bit builds when CONFIG_TIMER_STATS is selected.
    
timer_list is widely used across the kernel so many structures will
benefit and shrink in size.

For example, with my config on x86_64
	per_cpu_dm_data shrinks from 136 to 128 bytes
and
	ahci_port_priv shrinks from 1032 to 968 bytes.


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

---
patch against v2.6.35-rc6
compiled & tested on x86_64

regards
Richard


diff --git a/include/linux/timer.h b/include/linux/timer.h
index ea965b8..14a6fd4 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -24,9 +24,9 @@ struct timer_list {
 	int slack;
 
 #ifdef CONFIG_TIMER_STATS
+	int start_pid;
 	void *start_site;
 	char start_comm[16];
-	int start_pid;
 #endif
 #ifdef CONFIG_LOCKDEP
 	struct lockdep_map lockdep_map;


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