Re: [PATCH 1/1] selftests/proc: use RSS in /proc/pid/smaps_rollup tearing tests

[Suren Baghdasaryan]

On Wed, Oct 28, 2026 at 12:59 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> On Wed, Oct 28, 2026 at 12:42 PM Pedro Falcato <pfalcato@xxxxxxx> wrote:
> >
> > On Wed, Oct 28, 2026 at 10:14:19AM +0000, Pedro Falcato wrote:
> > > On Tue, Oct 27, 2026 at 10:13:12PM -0700, Suren Baghdasaryan wrote:
> > > > Pss metrics can be affected by map count even if VMA tree stays unchanged,
> > > > therefore test checking VMA tree integrity can't use them. Use Rss instead
> > > > and pre-populate the VMAs so that Rss changes if a VMA gets skipped or
> > > > double-counted.
> > > >
> > > > Fixes: ca5480fb53fa ("selftests/proc: add /proc/pid/smaps_rollup tearing tests")
> > > > Reported-by: kernel test robot <yi1.lai@xxxxxxxxx>
> > > > Closes: https://lore.kernel.org/oe-lkp/202610271934.fd287c3f-lkp@xxxxxxxxx
> > > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > >
> > > Reviewed-by: Pedro Falcato <pfalcato@xxxxxxx>
> >
> > Actually, now I'm wondering: isn't Rss also flaky if memory pressure occurs?
>
> True. Sashiko's findings are also interesting, so I'll need to figure
> out more robust ways to test smaps_rollup. I will post an update once
> I figure it out.

I posted an updated version at
https://lore.kernel.org/all/20261101154503.3203036-1-surenb@xxxxxxxxxx/
It should work under memory pressure and also address Sahiko's concerns.

> Andrew, if this test failure is causing issues in the meantime, please
> feel free to remove the ca5480fb53fa patch until I get a better
> version out.
> Thanks!
>
> >
> > --
> > Pedro