[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/kprobes.c b/arch/i386/kernel/kprobes.c
index af1d533..b85cfa3 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -363,7 +363,7 @@
" pushf\n"
/* skip cs, eip, orig_eax */
" subl $12, %esp\n"
- " pushl %gs\n"
+ " pushl %fs\n"
" pushl %ds\n"
" pushl %es\n"
" pushl %eax\n"
@@ -387,7 +387,7 @@
" popl %edi\n"
" popl %ebp\n"
" popl %eax\n"
- /* skip eip, orig_eax, es, ds, gs */
+ /* skip eip, orig_eax, es, ds, fs */
" addl $20, %esp\n"
" popf\n"
" ret\n");