Enhance perf to collect KVM guest os statistics fromhost side
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From: William Cohen on 18 Mar 2010 18:00 * Ingo Molnar <mingo(a)xxxxxxxx> wrote: > * Avi Kivity <avi(a)xxxxxxxxxx> wrote: > > > Monitoring guests from the host is useful for kvm developers, but less so > > for users. > > Guest space profiling is easy, and 'perf kvm' is not about that. (plain 'perf' > will work if a proper paravirt channel is opened to the host) > > I think you might have misunderstood the purpose and role of the 'perf kvm' > patch here? 'perf kvm' is aimed at KVM developers: it is them who improve KVM > code, not guest kernel users. > > Ingo The software performance events work fine in a KVM guest. Do the hardware performance events work in KVM guest environment? Last time I looked the results for the hardware counters were not sane. The values were seemingly random numbers. Something like the following. Performance counter stats for 'ls': 3.427434 task-clock-msecs # 0.046 CPUs 2 context-switches # 0.001 M/sec 0 CPU-migrations # 0.000 M/sec 218 page-faults # 0.064 M/sec 140737488355327 cycles # 41062056440.861 M/sec 68825777242116 instructions # 0.489 IPC 68825777242117 branches # 20080846849.893 M/sec 68825777242118 branch-misses # 100.000 % <not counted> cache-references <not counted> cache-misses The guest image is using 2.6.34-0.10.rc1.git0.fc14.it68 kernel and the host is Fedora-12 with a kernel built from 2.6.34-rc1-tip+ git tree running on Quad-Core AMD Opteron(tm) Processor 2350. Is there some combination of kernel/distribution/hardware that the hardware performance counters are suppose to work on? -Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |