From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f43.google.com (mail-qa0-f43.google.com [209.85.216.43]) by kanga.kvack.org (Postfix) with ESMTP id 156306B006C for ; Fri, 27 Feb 2015 07:43:24 -0500 (EST) Received: by mail-qa0-f43.google.com with SMTP id bm13so12486536qab.2 for ; Fri, 27 Feb 2015 04:43:23 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id i4si3904179qcz.48.2015.02.27.04.43.21 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Feb 2015 04:43:22 -0800 (PST) Message-ID: <54F06636.6080905@redhat.com> Date: Fri, 27 Feb 2015 07:42:30 -0500 From: Jon Masters MIME-Version: 1.0 Subject: Re: [PATCH V4 0/6] RCU get_user_pages_fast and __get_user_pages_fast References: <1411740233-28038-1-git-send-email-steve.capper@linaro.org> In-Reply-To: <1411740233-28038-1-git-send-email-steve.capper@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steve Capper , linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, linux@arm.linux.org.uk, linux-arch@vger.kernel.org, linux-mm@kvack.org Cc: will.deacon@arm.com, gary.robertson@linaro.org, christoffer.dall@linaro.org, peterz@infradead.org, anders.roxell@linaro.org, akpm@linux-foundation.org, dann.frazier@canonical.com, mark.rutland@arm.com, mgorman@suse.de, hughd@google.com On 09/26/2014 10:03 AM, Steve Capper wrote: > This series implements general forms of get_user_pages_fast and > __get_user_pages_fast in core code 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. > > I appreciate that the merge window is coming very soon, and am posting > this revision on the off-chance that it gets the nod for 3.18. (The changes > thus far have been minimal and the feedback I've got has been mainly > positive). Head's up: these patches are currently implicated in a rare-to-trigger hang that we are seeing on an internal kernel. An extensive effort is underway to confirm whether these are the cause. Will followup. Jon. -- 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