Re: [PATCH v1 3/8] migration: Introduce dirty-limit capability

[Hyman Huang]

在 2022/9/2 16:07, Markus Armbruster 写道:
> huangy81@chinatelecom.cn writes:
>
> > From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
> >
> > Introduce migration dirty-limit capability, which can
> > be turned on before live migration and limit dirty
> > page rate durty live migration.
> >
> > Introduce migrate_dirty_limit function to help check
> > if dirty-limit capability enabled during live migration.
> >
> > Meanwhile, refactor vcpu_dirty_rate_stat_collect
> > so that period can be configured instead of hardcoded.
> >
> > dirty-limit capability is kind of like auto-converge
> > but using dirty limit instead of traditional cpu-throttle
> > to throttle guest down. To enable this feature, turn on
> > the dirty-limit capability before live migration using
> > migratioin-set-capabilities, and set the parameters
>
> migrate-set-capabilities
>
> > "x-vcpu-dirty-limit-period", "vcpu-dirty-limit" suitably
>
> "x-vcpu-dirty-limit"
>
> > to speed up convergence.
> >
> > Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
>
> Hmm.  You make dirty-limiting as a whole a stable interface (evidence:
> capability "dirty-limit" is stable), but keep its two parameters
> unstable.  Rationale behind that?
Thanks Markus's comments. :)

x-vcpu-dirty-limit-period is an experimental parameter indeed, as to 
x-vcpu-dirty-limit, i think it's resonable to be a stable parameter.
These 2 parameters are introduced first time and none of them suffer 
heavily tests, so i also made vcpu-dirty-limit experimental last version.

For dirty-limit interface, it improves the vCPU computational 
performance during migration indeed(see the test results in cover 
letter), so it sounds ok to be an stable interface.

The 'x-vcpu-dirty-limit-period' parameter can be dropped, IMHO, after 
being proved insignificant for migration in the future, and meanwhile, 
x-vcpu-dirty-limit be made stable.

Since I don't have much experience to introducing fresh new interface,
any suggestions are welcome.

--
Best regard

Hyman Huang(黄勇)