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Re: [Qemu-devel] [PATCH] cpus: reset throttle_thread_scheduled after sle
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH] cpus: reset throttle_thread_scheduled after sleep |
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Date: |
Thu, 25 May 2017 17:52:36 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
On 19/05/2017 23:29, Felipe Franciosi wrote:
> Currently, the throttle_thread_scheduled flag is reset back to 0 before
> sleeping (as part of the throttling logic). Given that throttle_timer
> (well, any timer) may tick with a slight delay, it so happens that under
> heavy throttling (ie. close or on CPU_THROTTLE_PCT_MAX) the tick may
> schedule a further cpu_throttle_thread() work item after the flag reset,
> but before the previous sleep completed. This results on the vCPU thread
> sleeping continuously for potentially several seconds in a row.
>
> The chances of that happening can be drastically minimised by resetting
> the flag after the sleep.
True, on the other hand this may also increase the chance of not
sleeping at all.
How overcommitted was the host system?
Paolo
> Signed-off-by: Felipe Franciosi <address@hidden>
> Signed-off-by: Malcolm Crossley <address@hidden>