[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] compute performace problem
I turned on rrobin rack116-xen:~# xm dmesg | grep -i sched (XEN) Using scheduler: Round-Robin Scheduler (rrobin) and get the same range of execution times as with bvt: Run Time = 183.780 Run Time = 157.980 Run Time = 65.770 Run Time = 65.530 Run Time = 86.000 Run Time = 65.530 Run Time = 79.270 Run Time = 88.150 Run Time = 69.600 Run Time = 64.900 Run Time = 246.310 Run Time = 252.230 Run Time = 64.880 " Does the domU have the same amount of memory as the native Linux? Is Yes. I reran on native linux with 512MB and the job ran in 64s every time. " the native Linux running on a single cpu, just like the domU? Yes. The Dell1650 has 1 cpu installed, and no HT (PIII). I've seen the effect on dual P4s as well. " domU definitely quiescent apart from the mpi job? there are some background daemons like gmond and rwhod, but that is the same on all setups. " directly observed the app taking 250 seconds good question. I wondered the same thing so I now made the script ssh to the ntp server to print the date between each run. And ... yes the elasped times match the wallclock from the ntp server. " If the app is cpu-bound, there are no other apps running in the domain, " and no other domains contending for that cpu, then it is hard to " imagine where the slowdown coudl come from. agreed. If the native linux execution time wasn't so consistent, I'd blame the app. I sent mail upstream to the app authors to see if they have a suggestion. It is part of the CardioWave simulation of electical pulses that flow through the heart (http://cardiowave.duke.edu) I tried some tight loops and got consistent durations for time scales from fractions of a second to 2000 seconds. The loops are like this: time for ((i=0;i<100000;++i)); do : ;done Here are /proc stats during the app compute phase: xenU vmstat: procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 1 0 0 4584 456 248044 0 0 8 0 108 15 100 0 0 0 1 0 0 4584 456 248044 0 0 0 0 106 11 100 0 0 0 1 0 0 4584 456 248044 0 0 0 0 106 9 100 0 0 0 1 0 0 4584 456 248044 0 0 0 24 110 17 100 0 0 0 xen0 vmstat: procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 9108 1648 2324 10532 0 0 0 24 59 28 0 0 100 0 0 0 9108 1648 2324 10532 0 0 0 0 38 14 0 0 100 0 0 0 9108 1640 2332 10532 0 0 0 88 62 37 0 1 94 5 xenU interrupt per second: irq128: 0 Dynamic-irq misdire irq131: 0 Dynamic-irq blkif irq129: 0 Dynamic-irq ctrl-if irq132: 7 Dynamic-irq eth0 irq130: 100 Dynamic-irq timer xen0 interrupt per second: irq 1: 0 Phys-irq i8042 irq128: 0 Dynamic-irq misdire irq 6: 0 irq129: 0 Dynamic-irq ctrl-if irq 12: 0 irq130: 38 Dynamic-irq timer irq 14: 0 Phys-irq ide0 irq131: 0 Dynamic-irq console irq 17: 6 Phys-irq eth0 irq132: 0 Dynamic-irq net-be- irq 18: 6 Phys-irq aic7xxx irq133: 0 Dynamic-irq blkif-b irq 19: 0 Phys-irq aic7xxx irq134: 0 Dynamic-irq vif2.0 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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