On Wed, Sep 22, 2021 at 11:46:04AM -0400, Kent Overstreet wrote: > On Wed, Sep 22, 2021 at 11:08:58AM -0400, Johannes Weiner wrote: > > On Tue, Sep 21, 2021 at 05:22:54PM -0400, Kent Overstreet wrote: > > > - it's become apparent that there haven't been any real objections to the code > > > that was queued up for 5.15. There _are_ very real discussions and points of > > > contention still to be decided and resolved for the work beyond file backed > > > pages, but those discussions were what derailed the more modest, and more > > > badly needed, work that affects everyone in filesystem land > > > > Unfortunately, I think this is a result of me wanting to discuss a way > > forward rather than a way back. > > > > To clarify: I do very much object to the code as currently queued up, > > and not just to a vague future direction. > > > > The patches add and convert a lot of complicated code to provision for > > a future we do not agree on. The indirections it adds, and the hybrid > > state it leaves the tree in, make it directly more difficult to work > > with and understand the MM code base. Stuff that isn't needed for > > exposing folios to the filesystems. > > > > As Willy has repeatedly expressed a take-it-or-leave-it attitude in > > response to my feedback, I'm not excited about merging this now and > > potentially leaving quite a bit of cleanup work to others if the > > downstream discussion don't go to his liking. We're at a take-it-or-leave-it point for this pull request. The time for discussion was *MONTHS* ago. > > Here is the roughly annotated pull request: > > Thanks for breaking this out, Johannes. > > So: mm/filemap.c and mm/page-writeback.c - I disagree about folios not really > being needed there. Those files really belong more in fs/ than mm/, and the code > in those files needs folios the most - especially filemap.c, a lot of those > algorithms have to change from block based to extent based, making the analogy > with filesystems. > > I think it makes sense to drop the mm/lru stuff, as well as the mm/memcg, > mm/migrate and mm/workingset and mm/swap stuff that you object to - that is, the > code paths that are for both file + anonymous pages, unless Matthew has > technical reasons why that would break the rest of the patch set. Conceptually, it breaks the patch set. Anywhere that we convert back from a folio to a page, the guarantee of folios is weakened (and possibly violated). I don't think it makes sense from a practical point of view either; it's re-adding compound_head() calls that just don't need to be there. > That discussion can still happen... and there's still the potential to get a lot > more done if we're breaking open struct page and coming up with new types. I got > Matthew on board with what you wanted, re: using the slab allocator for larger > allocations Wait, no, you didn't. I think it's a terrible idea. It's just completely orthogonal to this patch set, so I don't want to talk about it.
