linux-kernel - Re: [PATCH v12 mm-new 06/15] khugepaged: introduce collapse_max_ptes

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Message-ID: <922e3416-c3b2-4335-8caa-7054b07f1315@lucifer.local>
Date: Tue, 28 Oct 2025 17:59:47 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Nico Pache <npache@...hat.com>, linux-kernel@...r.kernel.org,
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Subject: Re: [PATCH v12 mm-new 06/15] khugepaged: introduce
 collapse_max_ptes_none helper function

On Tue, Oct 28, 2025 at 06:49:48PM +0100, David Hildenbrand wrote:
> > > Hey Lorenzo,
> > >
> > > > I mean not to beat a dead horse re: v11 commentary, but I thought we were going
> > > > to implement David's idea re: the new 'eagerness' tunable, and again we're now just
> > > > implementing the capping at HPAGE_PMD_NR/2 - 1 thing again?
> > >
> > > I spoke to David and he said to continue forward with this series; the
> > > "eagerness" tunable will take some time, and may require further
> > > considerations/discussion.
> >
> > It would be good to communicate this in the patch, I wasn't aware he had said go
> > ahead with it. Maybe I missed the mail.
>
> Just to clarify: yes, I think we should find a way to move forward with this
> series without an eagerness toggle.

OK, let's please communicate this clearly in future. Maybe I missed the comms on
that.

>
> That doesn't imply that we'll be using the capping as proposed here (I hate
> it, it's just tricky to work around it for now).

OK well this is what I thought, that you hadn't meant that we should go ahead
with the logic completely unaltered from that which was explicitly pushed back
on in v10 I think.

We obviously need to figure out a way forward on this so let's get that
done as quickly as we can.

>
> And ideally, we can do that without any temporary tunables, because I'm sure
> it is a problem we can solve internally long-term.

I went into great detail replying on the relevant thread about this, that's
have that discussion there for sanity's sake.

>
> --
> Cheers
>
> David / dhildenb
>

Thanks, Lorenzo