Hello, This series implements general forms of get_user_pages_fast and __get_user_pages_fast and activates them for arm and arm64. These are required for Transparent HugePages to function correctly, as a futex on a THP tail will otherwise result in an infinite loop (due to the core implementation of __get_user_pages_fast always returning 0). Unfortunately, a futex on THP tail can be quite common for certain workloads; thus THP is unreliable without a __get_user_pages_fast implementation. This series may also be beneficial for direct-IO heavy workloads and certain KVM workloads. Changes since PATCH V2 are: * spelt `PATCH' correctly in the subject prefix this time. :-( * Added acks, tested-bys and reviewed-bys. * Cleanup of patch #6 with pud_pte and pud_pmd helpers. * Switched config option from HAVE_RCU_GUP to HAVE_GENERIC_RCU_GUP. Changes since PATCH V1 are: * Rebase to 3.17-rc1 * Switched to kick_all_cpus_sync as suggested by Mark Rutland. The main changes since RFC V5 are: * Rebased against 3.16-rc1. * pmd_present no longer tested for by gup_huge_pmd and gup_huge_pud, because the entry must be present for these leaf functions to be called. * Rather than assume puds can be re-cast as pmds, a separate function pud_write is instead used by the core gup. * ARM activation logic changed, now it will only activate RCU_TABLE_FREE and RCU_GUP when running with LPAE. The main changes since RFC V4 are: * corrected the arm64 logic so it now correctly rcu-frees page table backing pages. * rcu free logic relaxed for pre-ARMv7 ARM as we need an IPI to invalidate TLBs anyway. * rebased to 3.15-rc3 (some minor changes were needed to allow it to merge). * dropped Catalin's mmu_gather patch as that's been merged already. This series has been tested with LTP mm tests and some custom futex tests that exacerbate the futex on THP tail case; on both an Arndale board and a Juno board. Also debug counters were temporarily employed to ensure that the RCU_TABLE_FREE logic was behaving as expected. I would like to get this series into 3.18 as it fixes quite a big problem with THP on arm and arm64. This series is split into a core mm part, an arm part and an arm64 part. Could somebody please take patch #1 (if it looks okay)? Russell, would you be happy with patches #2, #3, #4? (if we get #1 merged) Catalin, would you be happy taking patches #5, #6? (if we get #1 merged) Cheers, -- Steve Steve Capper (6): mm: Introduce a general RCU get_user_pages_fast. arm: mm: Introduce special ptes for LPAE arm: mm: Enable HAVE_RCU_TABLE_FREE logic arm: mm: Enable RCU fast_gup arm64: mm: Enable HAVE_RCU_TABLE_FREE logic arm64: mm: Enable RCU fast_gup arch/arm/Kconfig | 5 + arch/arm/include/asm/pgtable-2level.h | 2 + arch/arm/include/asm/pgtable-3level.h | 15 ++ arch/arm/include/asm/pgtable.h | 6 +- arch/arm/include/asm/tlb.h | 38 ++++- arch/arm/mm/flush.c | 15 ++ arch/arm64/Kconfig | 4 + arch/arm64/include/asm/pgtable.h | 21 ++- arch/arm64/include/asm/tlb.h | 20 ++- arch/arm64/mm/flush.c | 15 ++ mm/Kconfig | 3 + mm/gup.c | 278 ++++++++++++++++++++++++++++++++++ 12 files changed, 412 insertions(+), 10 deletions(-) -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>