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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> |
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| .. | ||
| .gitignore | ||
| cacheflush.S | ||
| datapage.S | ||
| getcpu.S | ||
| gettimeofday.S | ||
| Makefile | ||
| note.S | ||
| sigtramp.S | ||
| vdso64_wrapper.S | ||
| vdso64.lds.S | ||