From owner-freebsd-arch@FreeBSD.ORG Wed Jan 21 14:19:21 2009 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 30F461065D12; Wed, 21 Jan 2009 14:19:21 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id EF93B8FC1E; Wed, 21 Jan 2009 14:19:20 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (pool-98-109-39-197.nwrknj.fios.verizon.net [98.109.39.197]) by cyrus.watson.org (Postfix) with ESMTPSA id 9D94546B03; Wed, 21 Jan 2009 09:19:20 -0500 (EST) Received: from localhost (john@localhost [127.0.0.1]) (authenticated bits=0) by server.baldwin.cx (8.14.3/8.14.3) with ESMTP id n0LEIsoI033505; Wed, 21 Jan 2009 09:19:14 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: freebsd-arch@freebsd.org Date: Wed, 21 Jan 2009 09:00:28 -0500 User-Agent: KMail/1.9.7 References: <20090118082145.GA18067@x2.osted.lan> <20090118140924.GA27264@x2.osted.lan> <20090118201202.674665B61@mail.bitblocks.com> In-Reply-To: <20090118201202.674665B61@mail.bitblocks.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200901210900.29226.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [127.0.0.1]); Wed, 21 Jan 2009 09:19:14 -0500 (EST) X-Virus-Scanned: ClamAV 0.94.2/8884/Wed Jan 21 08:15:32 2009 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: Kostik Belousov , Dag-Erling Sm?rgrav Subject: Re: stress2 is now in projects X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Jan 2009 14:19:28 -0000 On Sunday 18 January 2009 3:12:02 pm Bakul Shah wrote: > Allowing a user to specify the random seed (and *always* > reporting the random seed of every test) can't hurt and it > may actually gain you repeatability in some cases. Most bugs > are typically of garden variety, not dependent on some > complex interactions between parallel programs (or worse, on > processor heisenbugs). You can always try repeating a failing > test on a more deterministic set up like qemu etc. Actually, all the bugs I've used stress2 for were race conditions and locking bugs for which having a set random seed would not have helped. > One trick I have used in the past is to record "significant" > events in one or more ring buffers using some cheap encoding. > You have then access to past N events during any post kernel > crash analysis. This has far less of an overhead than debug > printfs and you can even leave it enabled in production use. man ktr -- John Baldwin