[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] compute performace problem
One of my users discovered large deviations in execution time for his mpi jobs on xenUs. I can reproduce the problem running his job on a single VM. On a native linux box the job completes in 64 secs +/- a second or so. On a xenU, it completes somewhere between 64 and 250 secs. This is true on 2.0.5 (2.6.10-xenU) and 2.0-testing(2.6.11-xenU). I tried xen-unstable but it seemed any task was taking 4 times as long as on 2.0 so I guess its still too unstable. Any suggestions I can try? Software is debian sarge with lam4-7.1.1 on xen-2.0-testing(Apr 22). stracing mpirun and lamd show no system calls being made during the computation phase, and that phase is where the extra time disappears. Starting and stopping do not cause the delay. xen is running the default bvt scheduler at default settings. Raising the priority of xenU made no difference. The domains on the box are an idle xen0 and the xenU running the app. /lib/tls is moved to tls.disabled on both domains, and on native linux. Hardware is a Dell PowerEdge 1650 (dual cpu sockets but only one cpu installed, 2GB mem). The app itself uses 375MB of mem. xenU was config for HIGHMEM4GB but was created with 640MB. No swap space is consumed on the system. I saw similar compute time variation running this job on a dual IBM x335. Raw results for 2.0-testing 2.6.11-xenU linux: Run Time = 104.590 Run Time = 247.370 Run Time = 89.050 Run Time = 64.090 Run Time = 63.430 Run Time = 80.360 Run Time = 64.410 Run Time = 131.070 Run Time = 236.850 Run Time = 75.470 Run Time = 134.570 Run Time = 65.350 Run Time = 65.480 Run Time = 64.970 Run Time = 202.650 Raw results for native 2.6.10 linux: Run Time = 64.120 Run Time = 63.170 Run Time = 63.540 Run Time = 64.670 Run Time = 64.990 Run Time = 64.070 Run Time = 64.930 Run Time = 64.640 Run Time = 64.030 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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