[PATCH] i386: Convert i386 PDA code to use %fs
Convert the PDA code to use %fs rather than %gs as the segment for
per-processor data. This is because some processors show a small but
measurable performance gain for reloading a NULL segment selector (as %fs
generally is in user-space) versus a non-NULL one (as %gs generally is).
On modern processors the difference is very small, perhaps undetectable.
Some old AMD "K6 3D+" processors are noticably slower when %fs is used
rather than %gs; I have no idea why this might be, but I think they're
sufficiently rare that it doesn't matter much.
This patch also fixes the math emulator, which had not been adjusted to
match the changed struct pt_regs.
[frederik.deweerdt@gmail.com: fixit with gdb]
[mingo@elte.hu: Fix KVM too]
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Ian Campbell <Ian.Campbell@XenSource.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Zachary Amsden <zach@vmware.com>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
diff --git a/include/asm-i386/pda.h b/include/asm-i386/pda.h
index 2ba2736..b12d59a 100644
--- a/include/asm-i386/pda.h
+++ b/include/asm-i386/pda.h
@@ -39,19 +39,19 @@
if (0) { T__ tmp__; tmp__ = (val); } \
switch (sizeof(_proxy_pda.field)) { \
case 1: \
- asm(op "b %1,%%gs:%c2" \
+ asm(op "b %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
break; \
case 2: \
- asm(op "w %1,%%gs:%c2" \
+ asm(op "w %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
break; \
case 4: \
- asm(op "l %1,%%gs:%c2" \
+ asm(op "l %1,%%fs:%c2" \
: "+m" (_proxy_pda.field) \
:"ri" ((T__)val), \
"i"(pda_offset(field))); \
@@ -65,19 +65,19 @@
typeof(_proxy_pda.field) ret__; \
switch (sizeof(_proxy_pda.field)) { \
case 1: \
- asm(op "b %%gs:%c1,%0" \
+ asm(op "b %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \
break; \
case 2: \
- asm(op "w %%gs:%c1,%0" \
+ asm(op "w %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \
break; \
case 4: \
- asm(op "l %%gs:%c1,%0" \
+ asm(op "l %%fs:%c1,%0" \
: "=r" (ret__) \
: "i" (pda_offset(field)), \
"m" (_proxy_pda.field)); \