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SubjectRe: [RFC][PATCH] Runtime switching of the idle function [take 2]

* 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.

Ingo
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