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| 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/kvm/book3s_exports.c | |
| parent | e6a74c6ea331b79c86e1898c504790b3dadc591d (diff) | |
| download | linux-18ad51dd342a7eb09dbcd059d0b451b616d4dafc.tar.gz linux-18ad51dd342a7eb09dbcd059d0b451b616d4dafc.tar.bz2 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/kvm/book3s_exports.c')
0 files changed, 0 insertions, 0 deletions