Hi Andrew, After discussion about this in Matthew's THP Cabal, we have decided to take a different approach with this patch set. Could you therefore remove it from mm-unstable, please? Sorry about the noise. I'm going to try 2 different approaches: - avoid the split lock contention by using mmu gather (suggested by Kirill) - expand the zap pte batching to also cover file folios (as requested by Yu). Thanks, Ryan On 27/07/2023 15:18, Ryan Roberts wrote: > Hi All, > > This is v4 of a small series in support of my work to enable the use of large > folios for anonymous memory (known as "FLEXIBLE_THP" or "LARGE_ANON_FOLIO") [5]. > It first makes it possible to add large, non-pmd-mappable folios to the deferred > split queue. Then it modifies zap_pte_range() to batch-remove spans of > physically contiguous pages from the rmap, which means that in the common case, > we elide the need to ever put the folio on the deferred split queue, thus > reducing lock contention and improving performance. > > This becomes more visible once we have lots of large anonymous folios in the > system, and Huang Ying has suggested solving this needs to be a prerequisit for > merging the main FLEXIBLE_THP/LARGE_ANON_FOLIO work. > > The series applies on top of v6.5-rc3 and a branch is available at [4]. > > NOTE: v3 is currently in mm-unstable and has a bug that affects s390, which this > version fixes. > > > Changes since v3 [3] > -------------------- > > - Fixed bug reported on s390 [6] > - Since s390 enables MMU_GATHER_NO_GATHER, __tlb_remove_page() causes a ref > to be dropped on the page, but we were still using the page after that > function call. > - Fix by using folio_get()/folio_put() to guarrantee lifetime of page > - Thanks to Nathan Chancellor for the bug report and helping me get set up > with s390! > - Don't use batch path if folio is not large > > > Changes since v2 [2] > -------------------- > > - patch 2: Reworked at Yu Zhou's request to reduce duplicated code. > - page_remove_rmap() now forwards to folio_remove_rmap_range() for the > !compound (PMD mapped) case. > - Both page_remove_rmap() and folio_remove_rmap_range() share common > epilogue via new helper function __remove_rmap_finish(). > - As a result of the changes, I've removed the previous Reviewed-bys. > - other 2 patches are unchanged. > > > Changes since v1 [1] > -------------------- > > - patch 2: Modified doc comment for folio_remove_rmap_range() > - patch 2: Hoisted _nr_pages_mapped manipulation out of page loop so its now > modified once per folio_remove_rmap_range() call. > - patch 2: Added check that page range is fully contained by folio in > folio_remove_rmap_range() > - patch 2: Fixed some nits raised by Huang, Ying for folio_remove_rmap_range() > - patch 3: Support batch-zap of all anon pages, not just those in anon vmas > - patch 3: Renamed various functions to make their use clear > - patch 3: Various minor refactoring/cleanups > - Added Reviewed-By tags - thanks! > > > [1] https://lore.kernel.org/linux-mm/20230717143110.260162-1-ryan.roberts@xxxxxxx/ > [2] https://lore.kernel.org/linux-mm/20230719135450.545227-1-ryan.roberts@xxxxxxx/ > [3] https://lore.kernel.org/linux-mm/20230720112955.643283-1-ryan.roberts@xxxxxxx/ > [4] https://gitlab.arm.com/linux-arm/linux-rr/-/tree/features/granule_perf/deferredsplit-lkml_v4 > [5] https://lore.kernel.org/linux-mm/20230714160407.4142030-1-ryan.roberts@xxxxxxx/ > [6] https://lore.kernel.org/linux-mm/20230726161942.GA1123863@dev-arch.thelio-3990X/ > > Thanks, > Ryan > > > Ryan Roberts (3): > mm: Allow deferred splitting of arbitrary large anon folios > mm: Implement folio_remove_rmap_range() > mm: Batch-zap large anonymous folio PTE mappings > > include/linux/rmap.h | 2 + > mm/memory.c | 132 +++++++++++++++++++++++++++++++++++++++++++ > mm/rmap.c | 125 ++++++++++++++++++++++++++++++---------- > 3 files changed, 229 insertions(+), 30 deletions(-) > > -- > 2.25.1 >
