Re: [PATCH 2/7] mm: shrinker: Add a .to_text() method for shrinkers

[Michal Hocko <mhocko@suse.com>]

On Mon 04-12-23 13:15:53, Kent Overstreet wrote:
> On Mon, Dec 04, 2023 at 11:33:12AM +0100, Michal Hocko wrote:
> > On Fri 01-12-23 16:25:06, Kent Overstreet wrote:
> > > On Fri, Dec 01, 2023 at 11:04:23AM +0100, Michal Hocko wrote:
> > > > On Thu 30-11-23 20:47:45, Kent Overstreet wrote:
> > > > > On Thu, Nov 30, 2023 at 09:14:35AM +0100, Michal Hocko wrote:
> > > > [...]
> > > > > > All that being said, I am with you on the fact that the oom report in
> > > > > > its current form could see improvements.
> > > > > 
> > > > > I'm glad we're finally in agreement on something!
> > > > > 
> > > > > If you want to share your own ideas on what could be improved and what
> > > > > you find useful, maybe we could find some more common ground.
> > > > 
> > > > One thing that I would consider an improvement is to have a way to
> > > > subscribe drivers with excessive memory consumption or those which are
> > > > struggling to dump their state.
> > > 
> > > Remember the memory allocation profiling patchset? The one where you
> > > kept complaining about "maintenancy overhead"?
> > 
> > Yes, I still maintain my opinion on that approach. I have never
> > questioned usefulness of the information.
> > 
> > > We can plug that into the show_mem report too, and list the top 10
> > > allocations by file and line number.
> > > 
> > > > Maybe your proposal can be extended that way but the crucial point is to
> > > > not dump all sorts of random shrinkers' state and end up with unwieldy
> > > > reports.  If, on the other hand, any particular shrinker struggles to
> > > > reclaim memory and it is sitting on a lot of memory it could be able to
> > > > flag itself to be involved in the dump.
> > > 
> > > Great, since as was mentioned in the original commit message it's not
> > > "all sorts of random shrinkers", but top 10 by objects reported, what
> > > I've got here should make you happy.
> > 
> > Can we do better and make that a shrinker decision rather than an
> > arbitrary top N selection? The thing is that shrinkers might even not
> > matter in many cases so their output would be just a balast. The number
> > of objects is not universaly great choice. As Dave mentioned metdata
> > might be pinning other objects.
> > 
> > That being said, if you want to give more debugability power to
> > shrinkers then it makes more sense to allow them to opt-in for the oom
> > report rather than control which of them to involve from the oom
> > reporting code which doesn't have enough context on its own.
> 
> If you've got an idea for a refinement, please submit your own patch and
> I'll look at incorporating it into the series.

OK, noted. Let me just remind you that /me as a reviewer have pointed
out several shortcomings of your proposed solution. From my POV this is
not something we should merge in its current form.

I am not going to comment further in this email thread as it seems you
are not interested in the review feedback and I have better things to do
than talking to /dev/null. This is not the first time you act like that
and I really do recommend you to think about your attitude and
communication style.

Good luck!
-- 
Michal Hocko
SUSE Labs