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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 28F538000D X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: fixjmywbsrcsayi3xmqfb111duo6g4j3 X-HE-Tag: 1701775862-2104 X-HE-Meta: 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 UeiDLf1T V4ntcdT/5c1BDM4oP77NQ7kLbz1NDEDl1J75oU1ZSS/ngb0DGCW2eoj8fSAoZL5dFn9M3/cwhqSvMnKOjvrEJ+EBrGxaHnSLiTR4xnIjI9CInXFvJJC/smfMR+5Oze9/6v/J6WNAH+hnYi8ntJYVLzw//YXfa1XxHGy46K6Iqiu2YozP8lVea60LmsHY0/mqrLwaAaMdIXQCQBsYDcFJw8OhK/UiEDK7eO8KBagHkbbDUVq2/lonE/PjnGDZaIYQi2lQm1xS6jveI3PbU3mtc9+KSlz7QR1fTdqQto2cJNHlUntI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04/12/2023 17:27, David Hildenbrand wrote: >> >> With rmap batching from [1] -- rebased+changed on top of that -- we could turn >> that into an effective (untested): >> >>           if (page && folio_test_anon(folio)) { >> +               nr = folio_nr_pages_cont_mapped(folio, page, src_pte, addr, end, >> +                                               pte, enforce_uffd_wp, &nr_dirty, >> +                                               &nr_writable); >>                   /* >>                    * If this page may have been pinned by the parent process, >>                    * copy the page immediately for the child so that we'll always >>                    * guarantee the pinned page won't be randomly replaced in the >>                    * future. >>                    */ >> -               folio_get(folio); >> -               if (unlikely(folio_try_dup_anon_rmap_pte(folio, page, >> src_vma))) { >> +               folio_ref_add(folio, nr); >> +               if (unlikely(folio_try_dup_anon_rmap_ptes(folio, page, nr, >> src_vma))) { >>                           /* Page may be pinned, we have to copy. */ >> -                       folio_put(folio); >> -                       return copy_present_page(dst_vma, src_vma, dst_pte, >> src_pte, >> -                                                addr, rss, prealloc, page); >> +                       folio_ref_sub(folio, nr); >> +                       ret = copy_present_page(dst_vma, src_vma, dst_pte, >> +                                               src_pte, addr, rss, prealloc, >> +                                               page); >> +                       return ret == 0 ? 1 : ret; >>                   } >> -               rss[MM_ANONPAGES]++; >> +               rss[MM_ANONPAGES] += nr; >>           } else if (page) { >> -               folio_get(folio); >> -               folio_dup_file_rmap_pte(folio, page); >> -               rss[mm_counter_file(page)]++; >> +               nr = folio_nr_pages_cont_mapped(folio, page, src_pte, addr, end, >> +                                               pte, enforce_uffd_wp, &nr_dirty, >> +                                               &nr_writable); >> +               folio_ref_add(folio, nr); >> +               folio_dup_file_rmap_ptes(folio, page, nr); >> +               rss[mm_counter_file(page)] += nr; >>           } >> >> >> We'll have to test performance, but it could be that we want to specialize >> more on !folio_test_large(). That code is very performance-sensitive. >> >> >> [1] https://lkml.kernel.org/r/20231204142146.91437-1-david@redhat.com > > So, on top of [1] without rmap batching but with a slightly modified version of Can you clarify what you mean by "without rmap batching"? I thought [1] implicitly adds rmap batching? (e.g. folio_dup_file_rmap_ptes(), which you've added in the code snippet above). > yours (that keeps the existing code structure as pointed out and e.g., updates > counter updates), running my fork() microbenchmark with a 1 GiB of memory: > > Compared to [1], with all order-0 pages it gets 13--14% _slower_ and with all > PTE-mapped THP (order-9) it gets ~29--30% _faster_. What test are you running - I'd like to reproduce if possible, since it sounds like I've got some work to do to remove the order-0 regression. > > So looks like we really want to have a completely seprate code path for > "!folio_test_large()" to keep that case as fast as possible. And "Likely" we > want to use "likely(!folio_test_large()". ;) Yuk, but fair enough. If I can repro the perf numbers, I'll have a go a reworking this. I think you're also implicitly suggesting that this change needs to depend on [1]? Which is a shame... I guess I should also go through a similar exercise for patch 2 in this series. > > Performing rmap batching on top of that code only slightly (another 1% or so) > improves performance in the PTE-mapped THP (order-9) case right now, in contrast > to other rmap batching. Reason is as all rmap code gets inlined here and we're > only doing subpage mapcount updates + PAE handling. >