Re: [RFC PATCH] mm: don't promote exclusive file folios of dying processes

[Barry Song <21cnbao@gmail.com>]

On Wed, Apr 16, 2025 at 4:32 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 12.04.25 10:58, Barry Song wrote:
> > From: Barry Song <v-songbaohua@oppo.com>
> >
> > Promoting exclusive file folios of a dying process is unnecessary and
> > harmful. For example, while Firefox is killed and LibreOffice is
> > launched, activating Firefox's young file-backed folios makes it
> > harder to reclaim memory that LibreOffice doesn't use at all.
>
> Do we know when it is reasonable to promote any folios of a dying process?
>

I don't know. It seems not reasonable at all. if one service crashes due to
SW bug, systemd will restart it immediately. this might be the case promoting
folios might be good. but it is really a bug of the service, not a normal case.

> Assume you restart Firefox, would it really matter to promote them when
> unmapping? New Firefox would fault-in / touch the ones it really needs
> immediately afterwards?

Usually users kill firefox to start other applications (users intend
to free memory
for new applications). For Android, an app might be killed because it has been
staying in the background inactively for a while.

On the other hand, even if users restart firefox immediately, their folios are
probably still in LRU to hit.

>
> --
> Cheers,
>
> David / dhildenb
>
Thanks
Barry