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Message-ID: <20081231214446.GA6856@localdomain>
Date: Wed, 31 Dec 2008 13:44:46 -0800
From: Ravikiran G Thirumalai <kiran@...lex86.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: linux-kernel@...r.kernel.org, travis@....com
Subject: [patch] x86: Fix incorrect __read_mostly on _boot_cpu_pda
The pda rework (commit 3461b0af025251bbc6b3d56c821c6ac2de6f7209)
to remove static boot cpu pdas introduced a 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@...lex86.org>
Index: linux-2.6/arch/x86/kernel/head64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head64.c 2008-12-30 15:28:08.000000000 -0800
+++ linux-2.6/arch/x86/kernel/head64.c 2008-12-31 10:36:21.000000000 -0800
@@ -27,7 +27,7 @@
#include <asm/trampoline.h>
/* boot cpu pda */
-static struct x8664_pda _boot_cpu_pda __read_mostly;
+static struct x8664_pda _boot_cpu_pda;
#ifdef CONFIG_SMP
/*
--
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