From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id DFE886B0037 for ; Wed, 29 Jan 2014 01:43:56 -0500 (EST) Received: by mail-pa0-f49.google.com with SMTP id hz1so1382450pad.8 for ; Tue, 28 Jan 2014 22:43:56 -0800 (PST) Received: from mga14.intel.com (mga14.intel.com. [143.182.124.37]) by mx.google.com with ESMTP id if4si1299423pbc.346.2014.01.28.22.43.55 for ; Tue, 28 Jan 2014 22:43:55 -0800 (PST) Date: Wed, 29 Jan 2014 14:43:50 +0800 From: Fengguang Wu 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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. -- 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