[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] performace issue when turn on apicv
>>> On 22.06.15 at 04:48, <jiangyifei@xxxxxxxxxx> wrote: > We found that all the events are HVM_EMUL_LAPIC_START_TIMER. The number of > TRC_HVM_EMUL_LAPIC_STOP_TIMER event is zero. > > Below is the details: > > apicv on: > TRC_HVM_EMUL_LAPIC_START_TIMER: count=111480 > TRC_HVM_EMUL_LAPIC_STOP_TIMER: count=0 > apicv off: > TRC_HVM_EMUL_LAPIC_START_TIMER: count=13595 > TRC_HVM_EMUL_LAPIC_STOP_TIMER: count=0 > > I want to know what the bad effects of create_periodic_time() being > repeatedly called are. Calling the function the way it is being done here, there is a drift in the time the next interrupt gets signaled, due to the delay incurred by the code doing the write emulation. See hvm/rtc.c (and its history) for further details as well as how the issue got addressed there. It would certainly be nice if you could see whether a similar approach can be taken (and would help) here. (A fundamental question, still unanswered, is over what time period these 111k timer adjustments happened - said problem matters only when there are many such updates in a relatively short period of time.) Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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