On Fri, 2007-03-16 at 19:14 +0100, Guillaume Chazarain wrote: > Hello, > > The scheduling problems I reported in the thread: > http://lkml.org/lkml/2007/3/3/128 > are caused by the set_cyc2ns_scale() function called when the CPU speed > changes. > Changing the scale causes a warp in the value returned by sched_clock(). > > The attached patch fixes the problem by adding an offset to the cyc2ns code to > smooth CPU frequency transitions. It also makes the cyc2ns parameters > per-CPU as cpufreq seems to support SMP but I don't have the hardware > to test. If you want > a version without the per-CPU or irqsave stuff, just ask.
Oh great! This has been a long standing issue I've never managed to get around to and your approach to fixing it is simpler then what I was thinking it would take. Thanks for knocking this off! > Although it solved all my scheduler issues, it may not be fully satisfactory > as for example my TSC can run at a frequency as low as 350 MHz when the CPU is > idle and slowed down to the max at 798 MHz by ondemand. So in this case, > sched_clock() does not return nanoseconds as it thinks it does. Hopefully this > is a non-issue as the scheduler is not stressed when the CPU is idle. Hmm.. It drops to 350MHz on idle, but only ~800Mhz by on-demand? That sounds more like the C3 idle TSC halt issue. > For me, this is needed in 2.6.21 if I want to be able to listen to music while > compiling a kernel using the ondemand governor. > > Thanks. > > Signed-off-by: Guillaume Chazarain <[EMAIL PROTECTED]> Acked-by: John Stultz <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
