Hi Christoffer, On 12/2/2015 3:42 PM, Mario Smarduch wrote: > > > On 12/2/2015 10:07 AM, Christoffer Dall wrote: >> Hi Mario, >> >> On Wed, Nov 18, 2015 at 06:20:03PM -0800, Mario Smarduch wrote: >>> Also with tick accounting enabled, and periodic timer HZ set to 1000 no irq time >>> is reported. That's with running a ping flood - 1200 int/s, not sure why >>> wouldn't any irq time be reported? The other two modes report irq time as expected. >>> >>> On 11/18/2015 11:46 AM, Mario Smarduch wrote: >>>> Hello, >>>> I noticed sched clock accounting can be enabled when arch-timer is >>>> initialized. But arm64 doesn't appear to have 'HAVE_IRQ_TIME_ACCOUNTING' >>>> selected (as of mainline 4.4-rc1) and IRQ_TIME_ACCOUNTING can't be selected. >>>> After adding it to arch/arm64/Kconfig, option appears to work fine. Depending on >>>> need all accounting options are fine, but irq time accounting appears to be most >>>> preferable. >>>> >>>> Any thoughts? Is it fine to enable it? >>>> >> Is any of this related to KVM? > > Indirectly, given the guest should yield same results. To be on the safe side I > ran the guest in all combinations (7) to confirm that's the case. > > Also verified that guest time on host appears fine in all these configurations. > It takes extra effort to get the guest time as opposed to other modes. > > - Mario >> >> -Christoffer >> > _______________________________________________ > kvmarm mailing list > kvmarm@xxxxxxxxxxxxxxxxxxxxx > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > While on this topic, one use case for RT like apps is run the host in full sched clock accounting mode/NO_HZ_FULL and guest in IRQ time accounting mode/NO_HZ_IDLE. This should make sense for a control plane, gateway guest (using normal IP stack, timers, ..) there you have a lot of transitions between run modes. ANd irq, softirq accounting matters. The host on the other side should be fine running a vCPU in full sched clock mode, you don't expect to many transitions from the vCPU, and less need for irq/softirq accounting if any. I recall you raised the point of run modes when you fixed guest time accounting, but I didn't have a good use case back then for your question. - Mario. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
