diff options
| author | Anton Blanchard <anton@samba.org> | 2012-07-04 20:37:11 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-07-11 14:18:40 +1000 |
| commit | 18ad51dd342a7eb09dbcd059d0b451b616d4dafc (patch) | |
| tree | 94809605669eb3b5e4e049501958a2fa93ae2de7 /arch/powerpc/kernel/smp.c | |
| parent | e6a74c6ea331b79c86e1898c504790b3dadc591d (diff) | |
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/kernel/smp.c')
| -rw-r--r-- | arch/powerpc/kernel/smp.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index e1417c42155c..0321007086f7 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -48,6 +48,7 @@ #ifdef CONFIG_PPC64 #include <asm/paca.h> #endif +#include <asm/vdso.h> #include <asm/debug.h> #ifdef DEBUG @@ -570,6 +571,8 @@ void __devinit start_secondary(void *unused) #ifdef CONFIG_PPC64 if (system_state == SYSTEM_RUNNING) vdso_data->processorCount++; + + vdso_getcpu_init(); #endif notify_cpu_starting(cpu); set_cpu_online(cpu, true); |