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Subject[patch 18/85] x86: fix incorrect __read_mostly on _boot_cpu_pda
2.6.27-stable review patch.  If anyone has any objections, please let us know.


From: Ravikiran G Thirumalai <>

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 <>
Acked-by: Mike Travis <>
Signed-off-by: Ingo Molnar <>
Signed-off-by: Greg Kroah-Hartman <>

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;


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