[Qemu-devel] Qemu and CPU wait time

[Qemu-devel] Qemu and CPU wait time

[Peter Lieven]

Hi,


is there something equivalent to "CPU ready" in VMWare or „Hyper-V Hypervisor Virtual Processor\CPU Wait Time Per Dispatch“ in Hyper-V in

KVM/Qemu?


Thanks,

Peter

Re: [Qemu-devel] Qemu and CPU wait time

[Stefan Hajnoczi]

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On Mon, Mar 06, 2017 at 03:32:49PM +0100, Peter Lieven wrote:
> is there something equivalent to "CPU ready" in VMWare or „Hyper-V Hypervisor Virtual Processor\CPU Wait Time Per Dispatch“ in Hyper-V in
> KVM/Qemu?

I think you can get this information from "perf sched latency" (see man
perf-sched).  Restrict it to the vcpu threads and it shows how long a
runnable vcpu has to wait (average and maximum).

Here is an example from https://lwn.net/Articles/353295/:

  perf sched record sleep 10     # record full system activity for 10 seconds
  perf sched latency --sort max  # report latencies sorted by max

  -----------------------------------------------------------------------------------------
   Task                  |   Runtime ms  | Switches | Average delay ms | Maximum delay ms |
  -----------------------------------------------------------------------------------------
   python:14049          |    114.694 ms |      125 | avg:    0.120 ms | max:    5.343 ms |
  ...
  -----------------------------------------------------------------------------------------
   TOTAL:                |   3144.817 ms |    11654 |
  ---------------------------------------------------

More info: http://www.brendangregg.com/blog/2017-03-16/perf-sched.html

Stefan

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