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| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2007-02-13 13:26:20 +0100 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2007-02-13 13:26:20 +0100 |
| commit | 464d1a78fbf8cf6c7fd970e7b3e2db50a320ce28 (patch) | |
| tree | 536d8a92976e675b484b35dec88d40c97fab8ac8 /arch/i386/kernel/head.S | |
| parent | 54413927f022292aeccadd268fbf1c0b42129945 (diff) | |
| download | op-kernel-dev-464d1a78fbf8cf6c7fd970e7b3e2db50a320ce28.zip op-kernel-dev-464d1a78fbf8cf6c7fd970e7b3e2db50a320ce28.tar.gz | |
[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>
Diffstat (limited to 'arch/i386/kernel/head.S')
| -rw-r--r-- | arch/i386/kernel/head.S | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S index cb9abdf..15336c8 100644 --- a/arch/i386/kernel/head.S +++ b/arch/i386/kernel/head.S @@ -319,12 +319,12 @@ is386: movl $2,%ecx # set MP movl %eax,%ds movl %eax,%es - xorl %eax,%eax # Clear FS and LDT - movl %eax,%fs + xorl %eax,%eax # Clear GS and LDT + movl %eax,%gs lldt %ax movl $(__KERNEL_PDA),%eax - mov %eax,%gs + mov %eax,%fs cld # gcc2 wants the direction flag cleared at all times pushl $0 # fake return address for unwinder |
