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[PATCH] i386: Convert i386 PDA code to use %fs

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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>
This commit is contained in:
Jeremy Fitzhardinge
2007-02-13 13:26:20 +01:00
committed by Andi Kleen
parent 54413927f0
commit 464d1a78fb
17 changed files with 99 additions and 103 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
include/asm-i386/pda.h
View File

@@ -39,19 +39,19 @@ extern struct i386_pda _proxy_pda;
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 @@ extern struct i386_pda _proxy_pda;
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)); \