[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/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c
index 65d7620..8f4afcc 100644
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -128,8 +128,8 @@
X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \
X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF)
- COPY_SEG(gs);
- GET_SEG(fs);
+ GET_SEG(gs);
+ COPY_SEG(fs);
COPY_SEG(es);
COPY_SEG(ds);
COPY(edi);
@@ -244,9 +244,9 @@
{
int tmp, err = 0;
- err |= __put_user(regs->xgs, (unsigned int __user *)&sc->gs);
- savesegment(fs, tmp);
- err |= __put_user(tmp, (unsigned int __user *)&sc->fs);
+ err |= __put_user(regs->xfs, (unsigned int __user *)&sc->fs);
+ savesegment(gs, tmp);
+ err |= __put_user(tmp, (unsigned int __user *)&sc->gs);
err |= __put_user(regs->xes, (unsigned int __user *)&sc->es);
err |= __put_user(regs->xds, (unsigned int __user *)&sc->ds);