diff options
| author | Anton Blanchard <anton@samba.org> | 2012-07-04 22:37:11 +0200 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-07-11 06:18:40 +0200 |
| commit | 18ad51dd342a7eb09dbcd059d0b451b616d4dafc (patch) | |
| tree | 94809605669eb3b5e4e049501958a2fa93ae2de7 /arch/powerpc/include/asm/vdso.h | |
| parent | powerpc: Add a symbol for hypervisor trampolines (diff) | |
| download | linux-18ad51dd342a7eb09dbcd059d0b451b616d4dafc.tar.xz linux-18ad51dd342a7eb09dbcd059d0b451b616d4dafc.zip | |
powerpc: Add VDSO version of getcpu
We have a request for a fast method of getting CPU and NUMA node IDs
from userspace. This patch implements a getcpu VDSO function,
similar to x86.
Ben suggested we use SPRG3 which is userspace readable. SPRG3 can be
modified by a KVM guest, so we save the SPRG3 value in the paca and
restore it when transitioning from the guest to the host.
I have a glibc patch that implements sched_getcpu on top of this.
Testing on a POWER7:
baseline: 538 cycles
vdso: 30 cycles
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/include/asm/vdso.h')
| -rw-r--r-- | arch/powerpc/include/asm/vdso.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h index dc0419b66f17..50f261bc3e95 100644 --- a/arch/powerpc/include/asm/vdso.h +++ b/arch/powerpc/include/asm/vdso.h @@ -22,6 +22,8 @@ extern unsigned long vdso64_rt_sigtramp; extern unsigned long vdso32_sigtramp; extern unsigned long vdso32_rt_sigtramp; +int __cpuinit vdso_getcpu_init(void); + #else /* __ASSEMBLY__ */ #ifdef __VDSO64__ |