From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f179.google.com (mail-we0-f179.google.com [74.125.82.179]) by kanga.kvack.org (Postfix) with ESMTP id 09B456B0035 for ; Thu, 21 Aug 2014 16:42:31 -0400 (EDT) Received: by mail-we0-f179.google.com with SMTP id u57so9699750wes.24 for ; Thu, 21 Aug 2014 13:42:31 -0700 (PDT) Received: from mail-wi0-f172.google.com (mail-wi0-f172.google.com [209.85.212.172]) by mx.google.com with ESMTPS id gh8si10688586wib.53.2014.08.21.13.42.29 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 21 Aug 2014 13:42:30 -0700 (PDT) Received: by mail-wi0-f172.google.com with SMTP id n3so9299108wiv.5 for ; Thu, 21 Aug 2014 13:42:29 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1408635812-31584-1-git-send-email-steve.capper@linaro.org> References: <1408635812-31584-1-git-send-email-steve.capper@linaro.org> Date: Thu, 21 Aug 2014 14:42:29 -0600 Message-ID: Subject: Re: [PATH V2 0/6] RCU get_user_pages_fast and __get_user_pages_fast From: Dann Frazier Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Steve Capper Cc: linux-arm-kernel , Catalin Marinas , linux@arm.linux.org.uk, linux-arch@vger.kernel.org, linux-mm@kvack.org, Will Deacon , gary.robertson@linaro.org, Christoffer Dall , peterz@infradead.org, anders.roxell@linaro.org, akpm@linux-foundation.org, Mark Rutland , mgorman@suse.de On Thu, Aug 21, 2014 at 9:43 AM, Steve Capper 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 > 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org