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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] 99% iowait on one core in 8 core processor
Just checked my /proc/interrupts: EVERY xen related thing (blkif-backend,the domUs, xhci_hcd, all xen-interfaces, evtchn:xenstored, evtchn:qemu-dm is all bound to cpu0, only zeros for the other cpu-cores.. Sys is debian wheezy, xen is current testing from hg, kernel is openSuse3.4.2 with the xen patches they ship with it.. will try your irqbalanced-suggestion next.. 2012/7/12 Ian Campbell <ian.campbell@xxxxxxxxxx>: > On Wed, 2012-07-11 at 09:56 -0400, Matthias wrote: >> Hi, >> >> I experianced the same. >> >> I figured the reason behind this has nothing to do with what (v)cpus >> you assign to the domUs. In fact, I think that the real reason is that >> all I/O emulation from the domUs (like HDD, Network and Stuff) is all >> handled by CPU0 of dom0, even in a multi-core-architecture. > > This should not be the case. I/O emulation is done by qemu running in > domain 0 and should be scheduled on any dom0 vcpu. If it is not then > this is something to investigate. Normally this would require explicit > admin action to pin the affinity of the process though. > > One easy thing to look at would be /proc/interrupts to check that the > irq associated with ioreq upcalls for each guest are being properly > balanced (if not the installing irqbalanced might help) > > Ian. > >> >> You can test this with trying something I/O intensive like a hdd >> benchmark in the domU and you will see the dom0-cpu0 utilization >> rising. >> >> Using PVHVM or GPLPV-Driver only reduces the amount of utilization but >> it is still handled by cpu0 only. Due to that fact i leave cpu0 to my >> dom0 alone and only assign the other cpu-cores to the domUs. >> >> >> Note: This is only an assumption I made after seeing my machines >> behaviour. If the above isn't true, please correct me. >> >> >> 2012/7/11 Rajesh Kumar <rajesh@xxxxxxxx>: >> > Hi All, >> > >> > We have a xen server and using 8 core processor. >> > >> > I can see that there is 99% iowait on only core 0. >> > >> > >> > 02:28:49 AM CPU %user %nice %sys %iowait %irq %soft %steal >> > %idle intr/s >> > 02:28:54 AM all 0.00 0.00 0.00 12.65 0.00 0.02 2.24 >> > 85.08 1359.88 >> > 02:28:54 AM 0 0.00 0.00 0.00 96.21 0.00 0.20 3.19 >> > 0.40 847.11 >> > 02:28:54 AM 1 0.00 0.00 0.00 6.41 0.00 0.00 9.42 >> > 84.17 219.56 >> > 02:28:54 AM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 >> > 100.00 2.59 >> > 02:28:54 AM 3 0.00 0.00 0.00 0.00 0.00 0.00 2.12 >> > 97.88 76.25 >> > 02:28:54 AM 4 0.00 0.00 0.00 0.00 0.00 0.00 1.20 >> > 98.80 118.56 >> > 02:28:54 AM 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 >> > 100.00 3.59 >> > 02:28:54 AM 6 0.00 0.00 0.00 0.00 0.00 0.00 2.02 >> > 97.98 89.62 >> > 02:28:54 AM 7 0.00 0.00 0.00 0.00 0.00 0.00 0.20 >> > 99.80 2.59 >> > >> > 02:28:54 AM CPU %user %nice %sys %iowait %irq %soft %steal >> > %idle intr/s >> > 02:28:59 AM all 0.00 0.00 0.00 12.48 0.00 0.00 2.78 >> > 84.74 1317.43 >> > 02:28:59 AM 0 0.00 0.00 0.00 98.80 0.00 0.00 0.80 >> > 0.40 885.17 >> > 02:28:59 AM 1 0.00 0.00 0.00 0.00 0.00 0.00 11.38 >> > 88.62 151.30 >> > 02:28:59 AM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.20 >> > 99.80 2.81 >> > 02:28:59 AM 3 0.00 0.00 0.00 0.00 0.00 0.00 7.21 >> > 92.79 94.79 >> > 02:28:59 AM 4 0.00 0.00 0.00 0.00 0.00 0.00 2.20 >> > 97.80 170.34 >> > 02:28:59 AM 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 >> > 100.00 4.41 >> > 02:28:59 AM 6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 >> > 100.00 5.81 >> > 02:28:59 AM 7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 >> > 100.00 2.81 >> > >> > >> > I have even tries changing the cpus mapped to the DomU with out no effect. >> > >> > Name CPU CPU Affinity >> > 4pulse 1 1 >> > 2music 3 3 >> > Domain-0 0 0 >> > Domain-0 1 1 >> > Domain-0 2 2 >> > Domain-0 3 3 >> > Domain-0 4 4 >> > Domain-0 5 5 >> > Domain-0 6 6 >> > Domain-0 7 7 >> > analshah 6 any cpu >> > arunvelayudhan 7 any cpu >> > backup 7 any cpu >> > crickruns 3 1-3 >> > crickruns 2 1-3 >> > crickruns 1 1-3 >> > crickruns 2 1-3 >> > crickruns 1 1-3 >> > crickruns 1 1-3 >> > dedicatedjv 7 any cpu >> > yeluthu 4 3-5 >> > yeluthu 3 3-5 >> > yeluthu 3 3-5 >> > yeluthu 3 3-5 >> > yeluthu 3 3-5 >> > yeluthu 3 3-5 >> > freshnfresh 3 any cpu >> > monitoring 7 any cpu >> > reporter 6 5-7 >> > reporter 7 5-7 >> > reporter 6 5-7 >> > reporter 6 5-7 >> > reporter 7 5-7 >> > reporter 7 5-7 >> > reporter 5 5-7 >> > reporter 7 5-7 >> > radio03 7 any cpu >> > saampeter 2 1-2 >> > saampeter 2 1-2 >> > >> > >> > Thanks, >> > Rajesh >> > _______________________________________________ >> > Xen-users mailing list >> > Xen-users@xxxxxxxxxxxxx >> > http://lists.xen.org/xen-users >> >> _______________________________________________ >> Xen-users mailing list >> Xen-users@xxxxxxxxxxxxx >> http://lists.xen.org/xen-users > > _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxx http://lists.xen.org/xen-users
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