[PATCH] i386: Convert i386 PDA code to use %fs
authorJeremy Fitzhardinge <jeremy@goop.org>
Tue, 13 Feb 2007 12:26:20 +0000 (13:26 +0100)
committerAndi Kleen <andi@basil.nowhere.org>
Tue, 13 Feb 2007 12:26:20 +0000 (13:26 +0100)
commit464d1a78fbf8cf6c7fd970e7b3e2db50a320ce28
tree536d8a92976e675b484b35dec88d40c97fab8ac8
parent54413927f022292aeccadd268fbf1c0b42129945
[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>
17 files changed:
arch/i386/kernel/asm-offsets.c
arch/i386/kernel/cpu/common.c
arch/i386/kernel/entry.S
arch/i386/kernel/head.S
arch/i386/kernel/kprobes.c
arch/i386/kernel/process.c
arch/i386/kernel/ptrace.c
arch/i386/kernel/signal.c
arch/i386/kernel/traps.c
arch/i386/kernel/vm86.c
arch/i386/math-emu/get_address.c
drivers/kvm/vmx.c
include/asm-i386/elf.h
include/asm-i386/mmu_context.h
include/asm-i386/pda.h
include/asm-i386/processor.h
include/asm-i386/ptrace.h