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

[Paolo Bonzini <pbonzini@redhat.com>]

On 31/07/2015 20:11, Jason J. Herne wrote:
>>>
>>
>> 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.
> 
> So, we made that change in v3 to eliminate the per cpu timer. With a per
> cpu timer we avoid this problem and we no longer need to worry about
> a throttle_thread_scheduled, and timers stacking. Paolo, you had originally
> argued in favor of this change. With what we know now, do you still think
> having only a single timer is best? Or should I switch back to a timer per
> cpu? With a timer per cpu we can simply reset the timer immediately after
> the sleep.

It's okay to have a single timer, only the formulas have to be
corrected: either you remove the pct/(1-pct) from the callback or you
add a /(1-pct) to the timer_mod.

Paolo