Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762706AbZAGWys (ORCPT ); Wed, 7 Jan 2009 17:54:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752904AbZAGWyh (ORCPT ); Wed, 7 Jan 2009 17:54:37 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:51270 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750889AbZAGWyf (ORCPT ); Wed, 7 Jan 2009 17:54:35 -0500 Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning From: Dave Kleikamp To: Linus Torvalds Cc: Peter Zijlstra , Steven Rostedt , paulmck@linux.vnet.ibm.com, Gregory Haskins , Ingo Molnar , Matthew Wilcox , Andi Kleen , Chris Mason , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich In-Reply-To: References: <87r63ljzox.fsf@basil.nowhere.org> <20090103191706.GA2002@parisc-linux.org> <1231242031.11687.97.camel@twins> <20090106121052.GA27232@elte.hu> <4963584A.4090805@novell.com> <20090106131643.GA15228@elte.hu> <1231248041.11687.107.camel@twins> <49636799.1010109@novell.com> <20090106214229.GD6741@linux.vnet.ibm.com> <1231278275.11687.111.camel@twins> <1231279660.11687.121.camel@twins> <1231281801.11687.125.camel@twins> <1231283778.11687.136.camel@twins> <1231329783.11687.287.camel@twins> <1231347442.11687.344.camel@twins> <1231365115.11687.361.camel@twins> Content-Type: text/plain Date: Wed, 07 Jan 2009 16:54:30 -0600 Message-Id: <1231368870.6686.16.camel@norville.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1091 Lines: 35 On Wed, 2009-01-07 at 13:58 -0800, Linus Torvalds wrote: > > On Wed, 7 Jan 2009, Peter Zijlstra wrote: > > > > Do we really have to re-do all that code every loop? > > No, you're right, we can just look up the cpu once. Which makes Andrew's > argument that "probe_kernel_address()" isn't in any hot path even more > true. Do you need to even do that if CONFIG_DEBUG_PAGEALLOC is unset? Something like: #ifdef CONFIG_DEBUG_PAGEALLOC /* * Need to access the cpu field knowing that * DEBUG_PAGEALLOC could have unmapped it if * the mutex owner just released it and exited. */ if (probe_kernel_address(&thread->cpu, cpu)) break; #else cpu = thread->cpu; #endif Shaggy -- David Kleikamp IBM Linux Technology Center -- 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/