[patch 16/94] x86: fix incorrect __read_mostly on _boot_cpu_pda

[Greg KH]

2.6.28-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Ravikiran G Thirumalai <kiran@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Acked-by: Mike Travis <travis@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/x86/kernel/head64.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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
 /*

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