From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756034AbaA2Gn4 (ORCPT ); Wed, 29 Jan 2014 01:43:56 -0500 Received: from mga03.intel.com ([143.182.124.21]:5328 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929AbaA2Gnz (ORCPT ); Wed, 29 Jan 2014 01:43:55 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,740,1384329600"; d="scan'208";a="466399215" Date: Wed, 29 Jan 2014 14:43:50 +0800 From: Fengguang Wu To: Dave Hansen Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com, pshelar@nicira.com Subject: Re: [PATCH] mm: slub: fix page->_count corruption (again) Message-ID: <20140129064350.GA20252@localhost> References: <20140128231722.E7387E6B@viggo.jf.intel.com> <20140128152956.d5659f56ae279856731a1ac5@linux-foundation.org> <52E842CF.7090102@sr71.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52E842CF.7090102@sr71.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 28, 2014 at 03:52:47PM -0800, Dave Hansen wrote: > On 01/28/2014 03:29 PM, Andrew Morton wrote: > > On Tue, 28 Jan 2014 15:17:22 -0800 Dave Hansen wrote: > > This code is borderline insane. > > No argument here. > > > Yes, struct page is special and it's worth spending time and doing > > weird things to optimise it. But sheesh. > > > > An alternative is to make that cmpxchg quietly go away. Is it more > > trouble than it is worth? > > It has measurable performance benefits, and the benefits go up as the > cost of en/disabling interrupts goes up (like if it takes you a hypercall). > > Fengguang, could you run a set of tests for the top patch in this branch > to see if we'd be giving much up by axing the code? > > https://github.com/hansendc/linux/tree/slub-nocmpxchg-for-Fengguang-20140128 Sure, I've queued tests for the branch. Will report back after 1-2 days. Thanks, Fengguang > I was talking with one of the distros about turning it off as well. > They mentioned that they saw a few performance regressions when it was > turned off. I'll share details when I get them.