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

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] Qemu and CPU wait time
Date: Wed, 22 Mar 2017 16:06:37 +0000
User-agent: Mutt/1.7.1 (2016-10-04)

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


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