Re: [RFC 0/4] Introduce unbalance proactive reclaim

[Michal Hocko]

On Thu 09-11-23 18:29:03, Huan Yang wrote:
> HI Michal Hocko,
> 
> Thanks for your suggestion.
> 
> 在 2023/11/9 17:57, Michal Hocko 写道:
> > [Some people who received this message don't often get email from mhocko@xxxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > 
> > On Thu 09-11-23 11:38:56, Huan Yang wrote:
> > [...]
> > > > If so, is it better only to reclaim private anonymous pages explicitly?
> > > Yes, in practice, we only proactively compress anonymous pages and do not
> > > want to touch file pages.
> > If that is the case and this is mostly application centric (which you
> > seem to be suggesting) then why don't you use madvise(MADV_PAGEOUT)
> > instead.
> Madvise  may not be applicable in this scenario.(IMO)
>
> This feature is aimed at a core goal, which is to compress the anonymous
> pages
> of frozen applications.
> 
> How to detect that an application is frozen and determine which pages can be
> safely reclaimed is the responsibility of the policy part.
> 
> Setting madvise for an application is an active behavior, while the above
> policy
> is a passive approach.(If I misunderstood, please let me know if there is a
> better
> way to set madvise.)

You are proposing an extension to the pro-active reclaim interface so
this is an active behavior pretty much by definition. So I am really not
following you here. Your agent can simply scan the address space of the
application it is going to "freeze" and call pidfd_madvise(MADV_PAGEOUT)
on the private memory is that is really what you want/need.

-- 
Michal Hocko
SUSE Labs