Re: [PATCH v2] mm: Add configuration to control whether vmpressure notifier is enabled

[Michal Hocko]

On Sun 22-08-21 17:46:08, yong w wrote:
> > All those reasons should be a part of the changelog.
> >....
> > I am not sure these are sufficient justifications but that is something
> > to discuss. And hence it should be a part of the changelog.
> >
> OK, These reasons will be added to the patch notesin later versions.
> 
> > > 3. In the case where the user does not need vmpressure,  vmpressure
> > > calculation is additional overhead.
> >
> > You should quantify that and argue why that overhead cannot be further
> > reduced without config/boot time knobs.
> >
> The test results of the previously used PFT tool may not be obvious.
> Is there a better way to quantify it?

This is a question for you to answer I am afraid. You want to add a
configuration option and (as explained) that is not free of cost from
the maintenance POV. There must a very good reason to do that.

> > > In some special scenes with tight memory, vmpressure will be executed
> > > frequently.we use "likely" and "inline"
> > > to improve the performance of the kernel, why not reduce some
> > > unnecessary calculations?
> >
> > I am all for improving the code. Is it possible to do it by other means?
> > E.g. reduce a potential overhead when there no events registered?
> Yes, the method you mentioned may be feasible, but it does not conflict
> with this patch.

It is not in conflict but runtime overhead reduction without more burden
on the configurability is usually a preferred approach.
-- 
Michal Hocko
SUSE Labs