From owner-freebsd-current@FreeBSD.ORG Thu Aug 21 13:56:56 2003 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 701EE16A4BF for ; Thu, 21 Aug 2003 13:56:56 -0700 (PDT) Received: from fledge.watson.org (fledge.watson.org [204.156.12.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id BBC5543FCB for ; Thu, 21 Aug 2003 13:56:55 -0700 (PDT) (envelope-from robert@fledge.watson.org) Received: from fledge.watson.org (localhost [127.0.0.1]) by fledge.watson.org (8.12.9/8.12.9) with ESMTP id h7LKulrO067137; Thu, 21 Aug 2003 16:56:47 -0400 (EDT) (envelope-from robert@fledge.watson.org) Received: from localhost (robert@localhost)h7LKulUp067134; Thu, 21 Aug 2003 16:56:47 -0400 (EDT) Date: Thu, 21 Aug 2003 16:56:47 -0400 (EDT) From: Robert Watson X-Sender: robert@fledge.watson.org To: cosmin In-Reply-To: <20030821204652.GA592@nacom.phy.uic.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: freebsd-current@freebsd.org Subject: Re: malloc message with nfs transfer X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Aug 2003 20:56:56 -0000 On Thu, 21 Aug 2003, cosmin wrote: > > Sorry, just to be clear -- is the message you're getting on the NFS > > client, or the NFS server? Could you turn on debug.witness_ddb and get a > > stack trace for the warning? > > This is on the NFS server. I turned on debug.witness_ddb, but I'm not > sure if this will help, because the system isn't locking up, or > otherwise stopping. I have tried setting a breakpoint in ddb for > 0xc4444ef0, but it starts breaking right away. The malloc() messages > are many minutes apart. With witness_ddb turned on, the kernel should drop into ddb whenever there's a witness-related warning, which should include the warnings you mentioned in your previous e-mail. > I'm not sure if these messages indicate anything critical. I was mainly > concerned with the nfs performance. Generally speaking, WITNESS warns about potential problems, as opposed to actual problems: i.e., it warns when a deadlock "would have occurred", if the timing had been just right. This was a warning that a potentially blocking activity was performed while holding a mutex, which is generally a bad idea. A little bit more detail on the strack trace should be sufficient to track it down. Turning off WITNESS should dramatically improve performance at the risk of lowering debugging output (maybe that's not a risk :-). Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Network Associates Laboratories