Re: [Qemu-devel] [PATCH v4 1/5] cpu: Provide vcpu throttling interface

[Jason J. Herne]

On 07/31/2015 01:16 PM, Paolo Bonzini wrote:
> On 31/07/2015 19:12, Jason J. Herne wrote:
> > >
> >
> > Throttle ratio is relative to CPU_THROTTLE_TIMESLICE. Take a look at how
> > throttle_ratio is used in the calculation:
> >
> > long sleeptime_ms = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE);
> >
> > A value of 1 means we sleep the same amount of time that we execute.
>
> But that doesn't work if your timer runs every CPU_THROTTLE_TIMESLICE
> milliseconds, and thus schedules async work every CPU_THROTTLE_TIMESLICE
> milliseconds.
>
> The timer would have to be scheduled every (throttle_ratio + 1) *
> CPU_THROTTLE_TIMESLICE milliseconds, i.e. CPU_THROTTLE_TIMESLICE /
> (1-pct) milliseconds.
>
> Paolo

Doh! Yep :). This problem is an artifact of moving the timer_mod from
cpu_throttle_thread into cpu_throttle_timer_tick. I'll have to go back
to the review comments and look at why that was done.

--
-- Jason J. Herne (address@hidden)