On Thu, Aug 21, 2014 at 02:42:29PM -0600, Dann Frazier wrote: > 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> > Thanks Dann, I've added your Tested-by to the mm and two arm64 patches. Cheers, -- Steve -- 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>