On Tue, 27 Jun 2023, David Hildenbrand wrote:

On 27.06.23 06:44, Hugh Dickins wrote:

quoted

On Mon, 26 Jun 2023, Vishal Moola (Oracle) wrote:

quoted

The MM subsystem is trying to shrink struct page. This patchset
introduces a memory descriptor for page table tracking - struct ptdesc.

...

quoted

  39 files changed, 686 insertions(+), 455 deletions(-)

I don't see the point of this patchset: to me it is just obfuscation of
the present-day tight relationship between page table and struct page.

Matthew already explained:

quoted

The intent is to get ptdescs to be dynamically allocated at some point
in the ~2-3 years out future when we have finished the folio project ...

So in a kindly mood, I'd say that this patchset is ahead of its time.
But I can certainly adapt to it, if everyone else sees some point to it.

I share your thoughts, that code churn which will help eventually in the far,
far future (not wanting to sound too pessimistic, but it's not going to be
there tomorrow ;) ).

However, if it's just the same as the other conversions we already did (e.g.,
struct slab), then I guess there is no reason to stop now -- the obfuscation
already happened.

... or is there a difference regarding this conversion and the previous ones?

I was aware of the struct slab thing, didn't see much point there myself
either; but it was welcomed by Vlastimil, and barely affected outside of
slab allocators, so I had no reason to object.

You think that if a little unnecessary churn (a *lot* of churn if you
include folios, which did save some repeated calls to compound_head())
has already occurred, that's a good precedent for allowing more and more?
My opinion happens to differ on that.

Hugh