Re: [PATCH 1/3] powernow-k6: disable cache when changing frequency

[Mikulas Patocka]

On Fri, 3 Jan 2014, Viresh Kumar wrote:

> On 2 January 2014 23:08, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> > Flushing the cache and changing frequency takes approximatelly 500us. The
> > patch increases policy->cpuinfo.transition_latency to that value.
> 
> Its not about how fast caches get cleaned but how much time would
> be wasted to get them filled again as same data could be required again
> which is just flushed out. That would impact performance more than
> flushing caches.

I didn't see any performance degradation when I tried changing the 
frequency manually with or without the cache flush patch - the overhead of 
running cpufreq (8ms) is far worse than the frequency transition itself.

Mikulas
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