From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f44.google.com (mail-wg0-f44.google.com [74.125.82.44]) by kanga.kvack.org (Postfix) with ESMTP id 551866B0035 for ; Fri, 22 Aug 2014 04:11:58 -0400 (EDT) Received: by mail-wg0-f44.google.com with SMTP id m15so10099916wgh.27 for ; Fri, 22 Aug 2014 01:11:57 -0700 (PDT) Received: from mail-wg0-f44.google.com (mail-wg0-f44.google.com [74.125.82.44]) by mx.google.com with ESMTPS id c9si44034096wja.128.2014.08.22.01.11.56 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 22 Aug 2014 01:11:56 -0700 (PDT) Received: by mail-wg0-f44.google.com with SMTP id m15so9992379wgh.3 for ; Fri, 22 Aug 2014 01:11:56 -0700 (PDT) Date: Fri, 22 Aug 2014 09:11:47 +0100 From: Steve Capper Subject: Re: [PATH V2 0/6] RCU get_user_pages_fast and __get_user_pages_fast Message-ID: <20140822081146.GA23364@linaro.org> References: <1408635812-31584-1-git-send-email-steve.capper@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dann Frazier 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 02:42:29PM -0600, Dann Frazier wrote: > 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 > 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org