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SubjectRe: [RFC][PATCH] Runtime switching of the idle function [take 2]
Ingo Molnar wrote:
> * Andrew Morton <akpm@osdl.org> wrote:
>
>
>>>The way to solve this was to set
>>> idle=poll. The original patch I sent was to allow the user to change to
>>> idle=poll dynamically. This way they could switch to the poll_idle and
>>> run there tests (requiring tsc not to drift) and then switch back to the
>>> default idle to save on electricity.
>>
>>Use gettimeofday()?
>>
>>If it's just for some sort of instrumentation, run NR_CPUS instances
>>of a niced-down busyloop, pin each one to a different CPU? That way
>>the idle function doesn't get called at all..
>
>
> idle=poll is also frequently done for performance reasons [it reduces
> idle wakeup latency by 10 usecs] - while it could be turned off if the
> system has been idle for some time. E.g. cpufreqd could sample idle time
> and turn on/off idle=poll. High-performance setups could enable it all
> the time.
>
> as long as it can be done with zero-cost, i dont see why Steven's patch
> wouldnt be a plus for us. It's a performance thing, and having runtime
> switches for seemless performance features cannot be bad.
>

Why not just slightly cleanup and extend (eg. to ACPI) the
hlt_counter thingy that many architectures already have?

Nick

--
SUSE Labs, Novell Inc.

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