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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
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4
include/asm-i386/elf.h
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@@ -90,8 +90,8 @@ typedef struct user_fxsr_struct elf_fpxregset_t;
pr_reg[6] = regs->eax; \
pr_reg[7] = regs->xds; \
pr_reg[8] = regs->xes; \
savesegment(fs,pr_reg[9]); \
pr_reg[10] = regs->xgs; \
pr_reg[9] = regs->xfs; \
savesegment(gs,pr_reg[10]); \
pr_reg[11] = regs->orig_eax; \
pr_reg[12] = regs->eip; \
pr_reg[13] = regs->xcs; \