Re: [PATCH v10 3/3] cpus-common: implement dirty page limit on virtual CPU

[Peter Xu]

On Wed, Dec 15, 2021 at 03:56:55PM +0800, Hyman Huang wrote:
> > > +{ 'command': 'vcpu-dirty-limit',
> > > +  'data': { 'enable': 'bool',
> > > +            '*cpu-index': 'uint64',
> > > +            '*dirty-rate': 'uint64'} }
> > 
> > Drop @enable, please.
> > 
> > If @dirty-rate is present, set the limit to its value.
> > 
> > If it's absent, cancel the limit.
> > 
> Ok. Indeed, this is the simplest style. :)
> 
> So the final qmp format should be like:
> 
> case 1: setup vcpu 0 dirty page limit 100MB/s
> vcpu-dirty-limit  cpu-index=0   dirty-rate=100MB/s
> 
> case 2: cancle vcpu 0 dirty page limit
> vcpu-dirty-limit  cpu-index=0

I actually agree with what you said... for human beings no one will read it as
"disable vcpu throttling", instead people could consider it enables vcpu
throttle with a default dirty rate from a gut feeling.

I think what Markus suggested is the simplest solution for computers, but it
can confuse human beings.  So it turns out to be a general question to QMP
scheme design: should we always assume QMP client to be a piece of software, or
should we still consider the feeling of human beings operating on QMP
interfaces using qmp-shell.

IMHO we should still consider the latter, if we don't lose much, anyway.  But I
don't have a strong opinion.

Thanks,

-- 
Peter Xu