x86: reduce CONFIG_X86_PPRO_FENCE bloat
CONFIG_X86_PPRO_FENCE bloats text:
i386 allmodconf: size mm/built-in.o
text data bss dec hex text ratio
vanilla: 163082 20372 40120 223574 36956 100.00%
bugfix : 163509 20372 40120 224001 36b01 0.26%
noppro : 162191 20372 40120 222683 365db - 0.55%
both : 162267 20372 40120 222759 36627 - 0.50% (+0.05% vs noppro)
So with the ppro memory ordering bug out of the way, the PG_uptodate fix
only adds 76 bytes of text.
allow this config to be specified by distros.
[ mingo@elte.hu: x86.git merge ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 018d68e..e09a6b7 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -321,8 +321,17 @@
depends on X86_32 && !M386
config X86_PPRO_FENCE
- def_bool y
+ bool "PentiumPro memory ordering errata workaround"
depends on M686 || M586MMX || M586TSC || M586 || M486 || M386 || MGEODEGX1
+ help
+ Old PentiumPro multiprocessor systems had errata that could cause memory
+ operations to violate the x86 ordering standard in rare cases. Enabling this
+ option will attempt to work around some (but not all) occurances of
+ this problem, at the cost of much heavier spinlock and memory barrier
+ operations.
+
+ If unsure, say n here. Even distro kernels should think twice before enabling
+ this: there are few systems, and an unlikely bug.
config X86_F00F_BUG
def_bool y
