Re: [PATCH v11 3/4] softmmu/dirtylimit: implement virtual CPU throttle

[Hyman Huang]

在 2022/1/19 20:16, Markus Armbruster 写道:
> huangy81@chinatelecom.cn writes:
>
> > From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> >
> > Setup a negative feedback system when vCPU thread
> > handling KVM_EXIT_DIRTY_RING_FULL exit by introducing
> > throttle_us_per_full field in struct CPUState. Sleep
> > throttle_us_per_full microseconds to throttle vCPU
> > if dirtylimit is enabled.
> >
> > Start a thread to track current dirty page rates and
> > tune the throttle_us_per_full dynamically untill current
> > dirty page rate reach the quota.
> >
> > Introduce the util function in the header for dirtylimit
> > implementation.
> >
> > Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
>
> [...]
>
> > diff --git a/qapi/migration.json b/qapi/migration.json
> > index bbfd48c..ac5fa56 100644
> > --- a/qapi/migration.json
> > +++ b/qapi/migration.json
> > @@ -1850,6 +1850,25 @@
> >   { 'command': 'query-dirty-rate', 'returns': 'DirtyRateInfo' }
> >   
> >   ##
> > +# @DirtyLimitInfo:
> > +#
> > +# Dirty page rate limit information of virtual CPU.
> > +#
> > +# @cpu-index: index of virtual CPU.
> > +#
> > +# @limit-rate: upper limit of dirty page rate for virtual CPU.
>
> Lacks a unit.  Is it bytes per second?  pages per second?
>
> If I understand your code correctly, zero means unlimited.  This is
> undocumented.  Please document it.  Something like "0 means unlimited"
> should do.
Ok.
> > +#
> > +# @current-rate: current dirty page rate for virtual CPU.
> > +#
> > +# Since: 7.0
> > +#
> > +##
> > +{ 'struct': 'DirtyLimitInfo',
> > +  'data': { 'cpu-index': 'int',
> > +            'limit-rate': 'int64',
> > +            'current-rate': 'int64' } }
>
> The next patch uses 'uint64' for set-vcpu-dirty-limit argument
> dirty-rate.  Why signed here?
Yes, this is not consistent with next patch. I left this wrongly after 
some modification, it should be moved in to next patch. I'll do that 
next version :(
> > +
> > +##
> >   # @snapshot-save:
> >   #
> >   # Save a VM snapshot
>
> [...]

--
Best regard

Hyman Huang(黄勇)