[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/traps.c b/arch/i386/kernel/traps.c
index 0efad8a..4ec2103 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -291,10 +291,11 @@
int i;
int in_kernel = 1;
unsigned long esp;
- unsigned short ss;
+ unsigned short ss, gs;
esp = (unsigned long) (®s->esp);
savesegment(ss, ss);
+ savesegment(gs, gs);
if (user_mode_vm(regs)) {
in_kernel = 0;
esp = regs->esp;
@@ -313,8 +314,8 @@
regs->eax, regs->ebx, regs->ecx, regs->edx);
printk(KERN_EMERG "esi: %08lx edi: %08lx ebp: %08lx esp: %08lx\n",
regs->esi, regs->edi, regs->ebp, esp);
- printk(KERN_EMERG "ds: %04x es: %04x ss: %04x\n",
- regs->xds & 0xffff, regs->xes & 0xffff, ss);
+ printk(KERN_EMERG "ds: %04x es: %04x fs: %04x gs: %04x ss: %04x\n",
+ regs->xds & 0xffff, regs->xes & 0xffff, regs->xfs & 0xffff, gs, ss);
printk(KERN_EMERG "Process %.*s (pid: %d, ti=%p task=%p task.ti=%p)",
TASK_COMM_LEN, current->comm, current->pid,
current_thread_info(), current, current->thread_info);