[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH][RESEND]RE: [Xen-devel] [PATCH] Fix softlockup issue after vcpu hotplug
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx] >Sent: 2007年1月30日 22:23 > >On 30/1/07 2:11 pm, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: > >> BTW, do you think whether it's worthy to destroy vcpu from >> scheduler when it's down and then re-init that vcpu into scheduler >> when it's on? I don't know whether this will make any influence to >> accounting of scheduler. Actually domain save/restore doesn't show >> this bug, and one obvious distinct compared to vcpu-hotplug is that >> domain is restored in a new context... > >I wouldn't expect this to make any significant difference to scheduling >accounting, certainly over a multi-second time period. > >Does the time you hoy-unplug the vcpu for make a difference to how >often you >see this problem? Did you try repro'ing with a 2.6.16 kernel? > > -- Keir Hi, Keir, I verified that attached patch does fix the issue by restricting max timeout to 1s. Either vcpu unplug/plug, or suspend cancel works fine. Actually domain runs well several hours after intensive testing. I also tried 2.6.16, and it's immune to this issue. I add some debug info in both 2.6.16 and 2.6.18, to print out delta value when delta > 1s. The results further proves our analysis. In 2.6.16, all the prints are: Delta 101 > HZ for cpuN Delta 101 > HZ for cpuN Delta 101 > HZ for cpuN ... While in 2.6.18, something like: Delta 199 > HZ for cpuN Delta 156 > HZ for cpuN Delta 192 > HZ for cpuN Delta 102 > HZ for cpuN ... After unplug/plug a cpu: Delta 951 > HZ for cpuN ... And then soflockup warning jumps out. So in 2.6.16, watchdog thread itself promises max timeout to about 1s by hooking a timer, while In 2.6.18, the max timeout value is volatile So I'm inclined to consider it as a fix, since there's no easy way to deduce an appropriate timeout without explicit/hard-code knowledge on such requirement like watchdog thread. How do you think? :-) P.S. The warning reported by Simon on 2.6.16 may be fixed by my previous patch, due to the late check. Thanks, Kevin Attachment:
fix_softlockup_2618.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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