Date: Wed, 1 Sep 2010 14:15:41 +0200 From: Gary Jennejohn <gljennjohn@googlemail.com> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-hackers@freebsd.org, FreeBSD-Current <freebsd-current@freebsd.org> Subject: Re: One-shot-oriented event timers management Message-ID: <20100901141541.3e36c868@ernst.jennejohn.org> In-Reply-To: <4C7E2E8A.3030709@FreeBSD.org> References: <4C7A5C28.1090904@FreeBSD.org> <20100830110932.23425932@ernst.jennejohn.org> <4C7B82EA.2040104@FreeBSD.org> <20100830121148.11926306@ernst.jennejohn.org> <20100831102918.4f5404cc@ernst.jennejohn.org> <4C7CC1DE.1080907@FreeBSD.org> <4C7E2E8A.3030709@FreeBSD.org>
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On Wed, 01 Sep 2010 13:44:26 +0300 Alexander Motin <mav@FreeBSD.org> wrote: > Alexander Motin wrote: > > Gary Jennejohn wrote: > >> On Mon, 30 Aug 2010 12:11:48 +0200 > >> OK, this is purely anecdotal, but I'll report it anyway. > >> > >> I was running pretty much all day with the patched kernel and things > >> seemed to be working quite well. > >> > >> Then, after about 7 hours, everything just stopped. > >> > >> I had gkrellm running and noticed that it updated only when I moved the > >> mouse. > >> > >> This behavior leads me to suspect that the timer interrupts had stopped > >> working and the mouse interrupts were causing processes to get scheduled. > >> > >> Unfortunately, I wasn't able to get a dump and had to hit reset to > >> recover. > >> > >> As I wrote above, this is only anecdotal, but I've never seen anything > >> like this before applying the patches. > > > > One-shot timers have one weak side: if for some reason timer interrupt > > getting lost -- there will be nobody to reload the timer. Such cases > > probably will require special attention. Same funny situation with > > mouse-driven scheduler happens also if LAPIC timer dies when pre-Core-iX > > CPU goes to C3 state. > > I have reproduced the problem locally. It happens more often when ticks > are not stopped on idle, like in your original case (or if explicitly > enabled by kern.eventtimer.idletick sysctl). > > I've made some changes to HPET driver, which, I hope, should fix > interrupt losses there. > > Updated patch: http://people.freebsd.org/~mav/timers_oneshot6.patch > > Patch also includes some optimizations to reduce lock contention. > > Thanks for testing. > OK, I'll give it a try, althought your previous patch seems to be working quite well. BTW I've also been using tm6292_idle.patch. Do I really need it? -- Gary Jennejohn
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