Hello, Thomas Gleixner wrote: > On Tue, 2007-06-26 at 17:00 +0200, Uwe Kleine-K??nig wrote: > > If I enable NO_HZ, the system jerks (I hope this is an understandable > > term ...). E.g. > > > > # time find /sys > > ... > > real 1m 19.52s > > user 0m 0.18s > > sys 0m 0.15s > > > > on a freshly booted machine. The output comes in several hunks with > > pausing between them. With no_hz=off, I get approx. the same. > > it's nohz=off not no_hz=off Currently I'm not sure, which I was really using. I think it was the right one, because dmesg changed. But anyhow, I will retest if I made it wrong. > > First I wondered why set_next_event is called twice between two timer > > interrupts most of the time. I found out that the timer is programed > > for the next tick in any case and if nothing needs the next tick, the > > interval is enlarged. I didn't spend time yet to check if it is > > easier/faster to only program the timer once. > > We optimize for the non-idle path, i.e. we keep the timer running as > long as we are not idle. Once we go idle we reprogram it. OK, sounds sane. > I looked at the patch and as far as I can understand it, there is > nothing obviously wrong about it. What a pity.
> One remark: why did you expand the clocksource to be 64 bit? The generic > code handles the 32 bit wrap already, so the expansion in your read > routine is adding overhead. The counter will wrap every 24 seconds, so > there is nothing to worry about. OK, I thought it to be better to have 64bit + some overhead. I will change that. > The behavior you are describing is might be related to some problem with > the clocksource readout, as the reprogramming values are calculated from > there. Any hints how I can debug that? Currently I cannot retest, but I will dig into it again and rereport. Thanks for your answer. Best regards Uwe -- Uwe Kleine-Koenig http://www.google.com/search?q=speed+of+light%3D - 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/
