From 18ad51dd342a7eb09dbcd059d0b451b616d4dafc Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 4 Jul 2012 20:37:11 +0000 Subject: 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 Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/smp.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/powerpc/kernel/smp.c') 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 #endif +#include #include #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); -- cgit v1.2.3