Now that the rmap overhaul[1] is upstream that provides a clean interface for rmap batching, let's implement PTE batching during fork when processing PTE-mapped THPs. This series is partially based on Ryan's previous work[2] to implement cont-pte support on arm64, but its a complete rewrite based on [1] to optimize all architectures independent of any such PTE bits, and to use the new rmap batching functions that simplify the code and prepare for further rmap accounting changes. We collect consecutive PTEs that map consecutive pages of the same large folio, making sure that the other PTE bits are compatible, and (a) adjust the refcount only once per batch, (b) call rmap handling functions only once per batch and (c) perform batch PTE setting/updates. While this series should be beneficial for adding cont-pte support on ARM64[2], it's one of the requirements for maintaining a total mapcount[3] for large folios with minimal added overhead and further changes[4] that build up on top of the total mapcount. Independent of all that, this series results in a speedup during fork with PTE-mapped THP, which is the default with THPs that are smaller than a PMD (for example, 16KiB to 1024KiB mTHPs for anonymous memory[5]). On an Intel Xeon Silver 4210R CPU, fork'ing with 1GiB of PTE-mapped folios of the same size (stddev < 1%) results in the following runtimes for fork() (shorter is better): Folio Size | v6.8-rc1 | New | Change ------------------------------------------ 4KiB | 0.014328 | 0.014265 | 0% 16KiB | 0.014263 | 0.013293 | - 7% 32KiB | 0.014334 | 0.012355 | -14% 64KiB | 0.014046 | 0.011837 | -16% 128KiB | 0.014011 | 0.011536 | -18% 256KiB | 0.013993 | 0.01134 | -19% 512KiB | 0.013983 | 0.011311 | -19% 1024KiB | 0.013986 | 0.011282 | -19% 2048KiB | 0.014305 | 0.011496 | -20% Next up is PTE batching when unmapping, that I'll probably send out based on this series this/next week. Only tested on x86-64. Compile-tested on most other architectures. Will do more testing and double-check the arch changes while this is getting some review. [1] https://lkml.kernel.org/r/20231220224504.646757-1-david@xxxxxxxxxx [2] https://lkml.kernel.org/r/20231218105100.172635-1-ryan.roberts@xxxxxxx [3] https://lkml.kernel.org/r/20230809083256.699513-1-david@xxxxxxxxxx [4] https://lkml.kernel.org/r/20231124132626.235350-1-david@xxxxxxxxxx [5] https://lkml.kernel.org/r/20231207161211.2374093-1-ryan.roberts@xxxxxxx Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Ryan Roberts <ryan.roberts@xxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxx> Cc: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxx> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx> Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> Cc: Sven Schnelle <svens@xxxxxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx Cc: linux-s390@xxxxxxxxxxxxxxx Cc: sparclinux@xxxxxxxxxxxxxxx David Hildenbrand (11): arm/pgtable: define PFN_PTE_SHIFT on arm and arm64 nios2/pgtable: define PFN_PTE_SHIFT powerpc/pgtable: define PFN_PTE_SHIFT risc: pgtable: define PFN_PTE_SHIFT s390/pgtable: define PFN_PTE_SHIFT sparc/pgtable: define PFN_PTE_SHIFT mm/memory: factor out copying the actual PTE in copy_present_pte() mm/memory: pass PTE to copy_present_pte() mm/memory: optimize fork() with PTE-mapped THP mm/memory: ignore dirty/accessed/soft-dirty bits in folio_pte_batch() mm/memory: ignore writable bit in folio_pte_batch() arch/arm/include/asm/pgtable.h | 2 + arch/arm64/include/asm/pgtable.h | 2 + arch/nios2/include/asm/pgtable.h | 2 + arch/powerpc/include/asm/pgtable.h | 2 + arch/riscv/include/asm/pgtable.h | 2 + arch/s390/include/asm/pgtable.h | 2 + arch/sparc/include/asm/pgtable_64.h | 2 + include/linux/pgtable.h | 17 ++- mm/memory.c | 188 +++++++++++++++++++++------- 9 files changed, 173 insertions(+), 46 deletions(-) base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d -- 2.43.0