From: Anton Blanchard Date: Wed, 4 Jul 2012 20:37:11 +0000 (+0000) Subject: powerpc: Add VDSO version of getcpu X-Git-Tag: v3.6-rc1~132^2~13 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18ad51dd342a7eb09dbcd059d0b451b616d4dafc;p=pandora-kernel.git 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 --- Reading git-diff-tree failed