On Thu, 2017-06-08 at 15:35:04 UTC, Nicholas Piggin wrote:
> After bc3551257a ("powerpc/64: Allow for relocation-on interrupts from
> guest to host"), a getppid() system call goes from 307 cycles to 358
> cycles (+17%) on POWER8. This is due significantly to the scratch SPR
> used by the hypercall
After bc3551257a ("powerpc/64: Allow for relocation-on interrupts from
guest to host"), a getppid() system call goes from 307 cycles to 358
cycles (+17%) on POWER8. This is due significantly to the scratch SPR
used by the hypercall check.
It turns out there are a some volatile registers common to
