On Thu, Aug 21, 2014 at 9:43 AM, Steve Capper <steve.capper@xxxxxxxxxx> wrote: > 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 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 really appreciate any comments (especially on the validity or > otherwise of the core fast_gup implementation) and testers. Continues to gets rid of my gccgo hang issue w/ THP. Tested-by: dann frazier <dann.frazier@xxxxxxxxxxxxx> > 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 | 11 +- > arch/arm64/include/asm/tlb.h | 20 ++- > arch/arm64/mm/flush.c | 15 ++ > mm/Kconfig | 3 + > mm/gup.c | 278 ++++++++++++++++++++++++++++++++++ > 12 files changed, 402 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>