Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754634Ab0AEOPi (ORCPT ); Tue, 5 Jan 2010 09:15:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754631Ab0AEOP2 (ORCPT ); Tue, 5 Jan 2010 09:15:28 -0500 Received: from one.firstfloor.org ([213.235.205.2]:52913 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753978Ab0AEOPZ (ORCPT ); Tue, 5 Jan 2010 09:15:25 -0500 To: Arjan van de Ven Cc: Peter Zijlstra , "Paul E. McKenney" , Peter Zijlstra , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "minchan.kim@gmail.com" , cl@linux-foundation.org, "hugh.dickins" , Nick Piggin , Ingo Molnar , Linus Torvalds Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() From: Andi Kleen References: <20100104182429.833180340@chello.nl> <20100104182813.753545361@chello.nl> <20100105054536.44bf8002@infradead.org> Date: Tue, 05 Jan 2010 15:15:15 +0100 In-Reply-To: <20100105054536.44bf8002@infradead.org> (Arjan van de Ven's message of "Tue, 5 Jan 2010 05:45:36 -0800") Message-ID: <87637gd4ek.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1036 Lines: 28 Arjan van de Ven writes: > On Mon, 04 Jan 2010 19:24:35 +0100 > Peter Zijlstra wrote: > >> Generic speculative fault handler, tries to service a pagefault >> without holding mmap_sem. > > > while I appreciate the goal of reducing contention on this lock... > wouldn't step one be to remove the page zeroing from under this lock? > that's by far (easily by 10x I would guess) the most expensive thing > that's done under the lock, and I would expect a first order of > contention reduction just by having the zeroing of a page not done > under the lock... The cache line bouncing of the shared cache lines hurts too. I suspect fixing this all properly will need some deeper changes. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/