[PATCH 8/9] arm64: support cpuidle-haltpoll

[Sudeep Holla]

On Tue, Apr 30, 2024 at 11:37:29AM -0700, Ankur Arora wrote:
> Add architectural support for the cpuidle-haltpoll driver by defining
> arch_haltpoll_*(). Also select ARCH_HAS_OPTIMIZED_POLL since we have
> an optimized polling mechanism via smp_cond_load*().
> 
> Add the configuration option, ARCH_CPUIDLE_HALTPOLL to allow
> cpuidle-haltpoll to be selected.
> 
> Note that we limit cpuidle-haltpoll support to when the event-stream is
> available. This is necessary because polling via smp_cond_load_relaxed()
> uses WFE to wait for a store which might not happen for an prolonged
> period of time. So, ensure the event-stream is around to provide a
> terminating condition.
>

Currently the event stream is configured 10kHz(1 signal per 100uS IIRC).
But the information in the cpuidle states for exit latency and residency
is set to 0(as per drivers/cpuidle/poll_state.c). Will this not cause any
performance issues ?

-- 
Regards,
Sudeep