From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752042AbaLQSwJ (ORCPT ); Wed, 17 Dec 2014 13:52:09 -0500 Received: from www.sr71.net ([198.145.64.142]:42395 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbaLQSwE (ORCPT ); Wed, 17 Dec 2014 13:52:04 -0500 Message-ID: <5491D0D2.5070103@sr71.net> Date: Wed, 17 Dec 2014 10:52:02 -0800 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Will Deacon , Linus Torvalds CC: Benjamin Herrenschmidt , Peter Zijlstra , Russell King - ARM Linux , Michal Simek , LKML , Linux-MM Subject: Re: post-3.18 performance regression in TLB flushing code References: <5490A5F8.6050504@sr71.net> <20141217100810.GA3461@arm.com> <20141217165310.GJ870@arm.com> In-Reply-To: <20141217165310.GJ870@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/17/2014 08:53 AM, Will Deacon wrote: > On Wed, Dec 17, 2014 at 04:28:23PM +0000, Linus Torvalds wrote: >> On Wed, Dec 17, 2014 at 2:08 AM, Will Deacon wrote: >> So why not just this trivial patch, to make the logic be the same it >> used to be (just using "end > 0" instead of the old "need_flush")? > > Looks fine to me... Dave? First of all, this is quite observable when testing single-threaded on a desktop. This is a mildly crusty Sandybridge CPU from 2011. I made 3 runs with a single thread: ./brk1_processes -s 30 -t 1 fb7332a9fed : 4323385 fb7332a9fed^: 4503736 fb7332a9fed+Linus's fix: 4516761 These things are also a little bit noisy, so we're well within the margin of error with Linus's fix. This also holds up on the large system.