powerpc: Use smt_snooze_delay=-1 to always busy loop
Right now if we want to busy loop and not give up any time to the hypervisor we put a very large value into smt_snooze_delay. This is sometimes useful when running a single partition and you want to avoid any latencies due to the hypervisor or CPU power state transitions. While this works, it's a bit ugly - how big a number is enough now we have NO_HZ and can be idle for a very long time. The patch below makes smt_snooze_delay signed, and a negative value means loop forever: echo -1 > /sys/devices/system/cpu/cpu0/smt_snooze_delay This change shouldn't affect the existing userspace tools (eg ppc64_cpu), but I'm cc-ing Nathan just to be sure. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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