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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A1C1A40008 X-Stat-Signature: qpbi36s889f7mzsnniwpnwaxjzza9akh X-HE-Tag: 1753348850-464007 X-HE-Meta: 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 tQP2ipnY 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 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 24.07.25 11:12, David Hildenbrand wrote: > On 24.07.25 11:09, Huan Yang wrote: >> >> 在 2025/7/24 16:59, David Hildenbrand 写道: >>> On 24.07.25 10:44, Huan Yang wrote: >>>> Summary >>>> == >>>> This patchset reuses page_type to store migrate entry count during the >>>> period from migrate entry setup to removal, enabling accelerated VMA >>>> traversal when removing migrate entries, following a similar >>>> principle to >>>> early termination when folio is unmapped in try_to_migrate. >>> >>> I absolutely detest (ab)using page types for that, so no from my side >>> unless I am missing something important. >>> >>>> >>>> In my self-constructed test scenario, the migration time can be reduced >>> >>> How relevant is that in practice? >> >> IMO, any folio mapped < nr vma in mapping(anon_vma, addresss_space), >> will benefit from this. >> >> So, all pages that have been COW-ed by child processes can be skipped. > > For small anon folios, you could use the anon-exclusive marker to derive > "there can only be a single mapping". > > It's stored alongside the migration entry. > > So once you restored that single migration entry, you can just stop the > walk. Essentially, something (untested) like this: diff --git a/mm/migrate.c b/mm/migrate.c index 425401b2d4e14..aa5bf96b1daee 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -421,6 +421,15 @@ static bool remove_migration_pte(struct folio *folio, /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, pvmw.address, pvmw.pte); + + /* + * If the small anon folio is exclusive, here can be exactly one + * page mapping -- the one we just restored. + */ + if (!folio_test_large(folio) && (rmap_flags & RMAP_EXCLUSIVE)) { + page_vma_mapped_walk_done(&pvmw); + break; + } } return true; -- Cheers, David / dhildenb