From: Ravikiran G Thirumalai <kiran@scalex86.org>
Date: Wed, 31 Dec 2008 21:44:46 +0000 (-0800)
Subject: x86: fix incorrect __read_mostly on _boot_cpu_pda
X-Git-Tag: v2.6.28.1~80
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ca0afb558614a8934427e8de3cf8c00168e384c4;p=karo-tx-linux.git

x86: fix incorrect __read_mostly on _boot_cpu_pda

commit 26799a63110dcbe81291ea53178f6b4810d07424 upstream.

The pda rework (commit 3461b0af025251bbc6b3d56c821c6ac2de6f7209)
to remove static boot cpu pdas introduced a performance bug.

_boot_cpu_pda is the actual pda used by the boot cpu and is definitely
not "__read_mostly" and ended up polluting the read mostly section with
writes.  This bug caused regression of about 8-10% on certain syscall
intensive workloads.

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Acked-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index d16084f90649..9461dc3d243c 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -26,7 +26,7 @@
 #include <asm/bios_ebda.h>
 
 /* boot cpu pda */
-static struct x8664_pda _boot_cpu_pda __read_mostly;
+static struct x8664_pda _boot_cpu_pda;
 
 #ifdef CONFIG_SMP
 /*