Date: Mon, 21 Jan 2013 12:09:21 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: freebsd-stable@freebsd.org, Ronald Klop <ronald-freebsd8@klop.yi.org> Subject: Re: time issues and ZFS Message-ID: <CAJ-Vmo=2Dmf4Lb-uoUQDrybyRSS=_bnV5KcNYGg5MnMxfhhu7w@mail.gmail.com> In-Reply-To: <1358783667.32417.434.camel@revolution.hippie.lan> References: <E1TxFcr-0006dx-MX@kabab.cs.huji.ac.il> <1358780588.32417.414.camel@revolution.hippie.lan> <E1TxJP2-000DS8-DJ@kabab.cs.huji.ac.il> <1358783667.32417.434.camel@revolution.hippie.lan>
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I still firmly believe the ACPI event timer code is racy, and what we may be seeing here is the fallout from that. It's very possible that we're missing interrupts here - the new eventtimer code that made it into 9.x puts the halt behind a critical section, with interrupts disabled. The only platforms that correctly implement enable-interrupts-and-halt atomically is the HLT (well, and the don't-sleep-at-all) idle loops on i386/amd64. The default method is to use the ACPI sleep method, which doesn't do atomic interrupt enable / halt. I'm still seeing odd stuff on some of my ACPI-using netbooks when doing net80211/ath development and it all goes away whenever I fondle with the above settings. So, play with kern.eventtimer.periodic, kern.eventtimer.idletick and machdep.idle (try setting machdep.idle to hlt, or something else listed in machdep.idle_available) - please report back what the results are. Adrian On 21 January 2013 07:54, Ian Lepore <ian@freebsd.org> wrote: > On Mon, 2013-01-21 at 17:35 +0200, Daniel Braniss wrote: >> ... >> > >> > What's the output of sysctl kern.eventtimer? >> >> kern.eventtimer.periodic is 0 >> >> > Does the bad behavior >> > change if you set kern.eventimer.periodic=1? >> > >> >> setting kern.eventtimer.timer=LAPIC >> instead of the default HPET made the missing cpu timers to appear: >> # vmstat -i >> interrupt total rate >> irq3: uart1 1695 0 >> irq4: uart0 5 0 >> irq19: ehci0 3875 0 >> irq20: hpet0 uhci3 5495755 1135 >> irq21: uhci2 ehci1 29 0 >> irq23: atapci0 48 0 >> cpu0:timer 7063 1 >> irq256: bce0 117073 24 >> irq260: mfi0 51083 10 >> irq261: mfi1 3088 0 >> cpu1:timer 484 0 >> cpu14:timer 36 0 >> cpu6:timer 486 0 >> cpu8:timer 38 0 >> cpu5:timer 38 0 >> cpu15:timer 38 0 >> cpu7:timer 32 0 >> cpu12:timer 38 0 >> cpu3:timer 40 0 >> cpu9:timer 36 0 >> cpu10:timer 34 0 >> cpu11:timer 37 0 >> cpu2:timer 33 0 >> cpu13:timer 40 0 >> cpu4:timer 36 0 >> Total 5681160 1173 >> >> is this relevant? > > I'll have to let someone who knows modern x86 hardware better comment on > the relative merits of hpet vs. lapic timers. If it was using hpet in > one-shot mode, and changing it to hpet in periodic mode makes the > problem go away, that might be a clue that there's something wrong in > the hpet eventtimer start or interrupt routines. > > I wonder if a single missed interrupt in one-shot mode would bring an > eventtimer to a halt like that? And if so, then what is it about > manually asking for the date that kicks it into running again? > > -- Ian > > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"
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