Messages in this thread | | | Subject | Re: [-rt] time-related problems with CPU frequency scaling | From | Lee Revell <> | Date | Mon, 17 Apr 2006 18:35:16 -0400 |
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On Sun, 2006-04-16 at 20:41 +0200, Wolfgang Hoffmann wrote: > - if CPU frequency is low when jackd is started, it complains: > "delay of 2915.000 usecs exceeds estimated spare > time of 2847.000; restart ..." > as soon as frequency is scaled up. Seems that jackd gets confused by some > influence of CPU frequency on timekeeping? No problems as long as CPU > frequency isn't scaled up, though.
JACK still uses the TSC for timing and thus is incompatible with CPU frequency scaling. You must use the -clockfix branch from CVS.
> - values in /proc/sys/kernel/preempt_max_latency scales inverse to > CPU frequency, i.e. 24us with CPU @ 800MHz and 12us with CPU @ 1,6GHz
This is normal - code that takes 12us to run at 1.6 GHz will take 24us at 800MHz. TANSTAAFL ;-)
Lee
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