Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755425Ab0BFLYh (ORCPT ); Sat, 6 Feb 2010 06:24:37 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:45987 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754614Ab0BFLYg (ORCPT ); Sat, 6 Feb 2010 06:24:36 -0500 Subject: Re: [PATCH 10/11] tracing/perf: Fix lock events recursions in the fast path From: Peter Zijlstra To: Frederic Weisbecker Cc: Ingo Molnar , Lai Jiangshan , paulmck@linux.vnet.ibm.com, LKML , Arnaldo Carvalho de Melo , Steven Rostedt , Paul Mackerras , Hitoshi Mitake , Li Zefan , Masami Hiramatsu , Jens Axboe In-Reply-To: <20100206111209.GC5062@nowhere> References: <1265188475-23509-1-git-send-regression-fweisbec@gmail.com> <1265188475-23509-11-git-send-regression-fweisbec@gmail.com> <20100204154700.GE6676@linux.vnet.ibm.com> <4B6B84A1.60805@cn.fujitsu.com> <1265363102.22001.286.camel@laptop> <1265363441.22001.300.camel@laptop> <20100205104937.GB29515@elte.hu> <1265371808.22001.502.camel@laptop> <1265371973.22001.508.camel@laptop> <1265374915.22001.562.camel@laptop> <20100206111209.GC5062@nowhere> Content-Type: text/plain; charset="UTF-8" Date: Sat, 06 Feb 2010 12:24:02 +0100 Message-ID: <1265455442.30057.499.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1131 Lines: 25 On Sat, 2010-02-06 at 12:12 +0100, Frederic Weisbecker wrote: > That said, I think this is good for a first step, but we can't continue > to force the lock events -> lockdep dependency in the long term. We > can't have a serious lock profiling if we are doomed to suffer the > slowness due to lockdep checks at the same time. > > Sure we can continue to support having both, but I think we should also > think about a solution to handle lock events without it in the future. > That will require some minimal lockdep functionalities (keeping the > lockdep map, and class hashes). You mean like building without CONFIG_PROVE_LOCKING, or boot with lockdep.prove_locking=0, or use echo 0 > /sys/modules/lockdep/prove_locking ? That keeps the lock tracking but does away with all the dependency analysis and was created for just such an use case as you are looking at, namely lockstat. -- 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/