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authorAnton Blanchard <anton@samba.org>2012-07-04 20:37:11 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2012-07-11 14:18:40 +1000
commit18ad51dd342a7eb09dbcd059d0b451b616d4dafc (patch)
tree94809605669eb3b5e4e049501958a2fa93ae2de7 /arch/powerpc/kernel/smp.c
parente6a74c6ea331b79c86e1898c504790b3dadc591d (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.c3
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);