Re: [RFC PATCH v2 00/11] add shmem mTHP collapse support

[Lorenzo Stoakes <ljs@kernel.org>]

On Thu, Jun 11, 2026 at 07:46:55PM +0800, Baolin Wang wrote:
> Hi Lorenzo,
>
> On 6/11/26 2:18 PM, Lorenzo Stoakes wrote:
> > On Wed, Jun 10, 2026 at 06:29:08PM +0800, Baolin Wang wrote:
> > > (Note: this patchset is not targeting v7.2, but posted for early feedback.)
> >
> > Hi Baolin,
> >
> > Speaking broadly, and to repeat what I said to Nico - I'd like to
> > re-emphasise my _strong_ desire for us to pay down technical debt in THP
> > code before adding any further major features.
> >
> > Really I'd have liked to see us do this _before_ khugepaged mTHP, but I
> > didn't want to put Nico through more than he already endured with that
> > series :)
> >
> > So I'd really like to see some action on that before we embark on any
> > further significant changes.
> >
> > This is no comment on your changes, just something that we really need to
> > address in THP generally.
> >
> > Will try to give some detailed commentary on the actual changes when I have
> > time also :)
>
> I fully understand the current state of THP maintenance, which is why this
> is an RFC. I’m not expecting it to be merged into mainline quickly (but
> thanks to Lance for the comments).

Ack, well maybe you'd be surprised if I didn't mention it ;)

And I will try to have a look through on basis of the technical changes!

>
> Also, as Nico noted, it might be worth reviewing the mTHP collapse selftests
> in this series firstly? as they can help validate the anonymous mTHP
> collapse path for future changes.

Yeah that sounds like a plan and thank you for writing them :) more testing is
welcome and very much appreciated.

Cheers, Lorenzo