From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f45.google.com (mail-pb0-f45.google.com [209.85.160.45]) by kanga.kvack.org (Postfix) with ESMTP id A71DF6B0031 for ; Tue, 28 Jan 2014 18:52:56 -0500 (EST) Received: by mail-pb0-f45.google.com with SMTP id un15so1009344pbc.18 for ; Tue, 28 Jan 2014 15:52:56 -0800 (PST) Received: from blackbird.sr71.net ([2001:19d0:2:6:209:6bff:fe9a:902]) by mx.google.com with ESMTP id fl7si278642pad.142.2014.01.28.15.52.50 for ; Tue, 28 Jan 2014 15:52:50 -0800 (PST) Message-ID: <52E842CF.7090102@sr71.net> Date: Tue, 28 Jan 2014 15:52:47 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH] mm: slub: fix page->_count corruption (again) References: <20140128231722.E7387E6B@viggo.jf.intel.com> <20140128152956.d5659f56ae279856731a1ac5@linux-foundation.org> In-Reply-To: <20140128152956.d5659f56ae279856731a1ac5@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com, pshelar@nicira.com, Wu Fengguang 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 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