On 05/12/2023 09:56, David Hildenbrand wrote: >>> >>> Ryan has series where we would make use of folio_remove_rmap_ptes() [1] >>> -- he carries his own batching variant right now -- and >>> folio_try_dup_anon_rmap_ptes()/folio_dup_file_rmap_ptes() [2]. >> >> Note that the contpte series at [2] has a new patch in v3 (patch 2), which could >> benefit from folio_remove_rmap_ptes() or equivalent. My plan was to revive [1] >> on top of [2] once it is merged. >> >>> >>> There is some overlap with both series (and some other work, like >>> multi-size THP [3]), so that will need some coordination, and likely a >>> stepwise inclusion. >> >> Selfishly, I'd really like to get my stuff merged as soon as there is no >> technical reason not to. I'd prefer not to add this as a dependency if we can >> help it. > > It's easy to rework either series on top of each other. The mTHP series has > highest priority, > no question, that will go in first. Music to my ears! It would be great to either get a reviewed-by or feedback on why not, for the key 2 patches in that series (3 & 4) and also your opinion on whether we need to wait for compaction to land (see cover letter). It would be great to get this into linux-next ASAP IMHO. > > Regarding the contpte, I think it needs more work. Especially, as raised, to not > degrade > order-0 performance. Maybe we won't make the next merge window (and you already > predicated > that in some cover letter :P ). Let's see. Yeah that's ok. I'll do the work to fix the order-0 perf. And also do the same for patch 2 in that series - would also be really helpful if you had a chance to look at patch 2 - its new for v3. > > But again, the conflicts are all trivial, so I'll happily rebase on top of > whatever is > in mm-unstable. Or move the relevant rework to the front so you can just carry > them/base on them. (the batched variants for dup do make the contpte code much > easier) So perhaps we should aim for mTHP, then this, then contpte last, benefiting from the batching. > > [...] > >>> >>> >>> New (extended) hugetlb interface that operate on entire folio: >>> * hugetlb_add_new_anon_rmap() -> Already existed >>> * hugetlb_add_anon_rmap() -> Already existed >>> * hugetlb_try_dup_anon_rmap() >>> * hugetlb_try_share_anon_rmap() >>> * hugetlb_add_file_rmap() >>> * hugetlb_remove_rmap() >>> >>> New "ordinary" interface for small folios / THP:: >>> * folio_add_new_anon_rmap() -> Already existed >>> * folio_add_anon_rmap_[pte|ptes|pmd]() >>> * folio_try_dup_anon_rmap_[pte|ptes|pmd]() >>> * folio_try_share_anon_rmap_[pte|pmd]() >>> * folio_add_file_rmap_[pte|ptes|pmd]() >>> * folio_dup_file_rmap_[pte|ptes|pmd]() >>> * folio_remove_rmap_[pte|ptes|pmd]() >> >> I'm not sure if there are official guidelines, but personally if we are >> reworking the API, I'd take the opportunity to move "rmap" to the front of the >> name, rather than having it burried in the middle as it is for some of these: >> >> rmap_hugetlb_*() >> >> rmap_folio_*() > > No strong opinion. But we might want slightly different names then. For example, > it's "bio_add_folio" and not "bio_folio_add": > > > rmap_add_new_anon_hugetlb() > rmap_add_anon_hugetlb() > ... > rmap_remove_hugetlb() > > > rmap_add_new_anon_folio() > rmap_add_anon_folio_[pte|ptes|pmd]() > ... > rmap_dup_file_folio_[pte|ptes|pmd]() > rmap_remove_folio_[pte|ptes|pmd]() > > Thoughts? Having now reviewed your series, I have a less strong opinion, perhaps it's actually best with your original names; "folio" is actually the subject after all; it's the thing being operated on. > >> >> I guess reading the patches will tell me, but what's the point of "ptes"? Surely >> you're either mapping at pte or pmd level, and the number of pages is determined >> by the folio size? (or presumably nr param passed in) > > It's really (currently) one function to handle 1 vs. multiple PTEs. For example: > > void folio_remove_rmap_ptes(struct folio *, struct page *, unsigned int nr, > struct vm_area_struct *); > #define folio_remove_rmap_pte(folio, page, vma) \ > folio_remove_rmap_ptes(folio, page, 1, vma) > void folio_remove_rmap_pmd(struct folio *, struct page *, > struct vm_area_struct *); Yeah now that I've looked at the series, this makes sense. "ptes" was originally making me think of contpte, but I suspect I'll be the only one with that association :) > > > Once could let the compiler generate specialized variants for the single-pte > versions to make the order-0 case faster. For now it's just a helper macro. >
