From: Trond Myklebust Subject: Re: [RFC][PATCH 0/5] NFS: trace points added to mounting path Date: Wed, 21 Jan 2009 17:56:10 -0500 Message-ID: <1232578570.7692.96.camel@heimdal.trondhjem.org> References: <4970B451.4080201@RedHat.com> <5B2817A2-B0FF-4FB5-9244-9E13C55EF6B2@oracle.com> <497757D1.7090908@RedHat.com> <49777988.6010401@RedHat.com> <4977A385.8000406@melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Chuck Lever , Linux NFS Mailing list , Linux NFSv4 mailing list , SystemTAP To: Greg Banks Return-path: Received: from mail-out1.uio.no ([129.240.10.57]:49925 "EHLO mail-out1.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751503AbZAUW4S (ORCPT ); Wed, 21 Jan 2009 17:56:18 -0500 In-Reply-To: <4977A385.8000406-cP1dWloDopni96+mSzHFpQC/G2K4zDHf@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, 2009-01-22 at 09:36 +1100, Greg Banks wrote: > Chuck Lever wrote: > > > > > > I think we need to visit this issue on a case-by-case basis. > > Sometimes dprintk is appropriate. Sometimes printk(KERN_ERR). > > Sometimes a performance metric. > Well said. > > > Trond has always maintained that dprintk() is best for developers, but > > probably inappropriate for field debugging, > It's not a perfect tool but it beats nothing at all. > > and I think that may also > > apply to trace points. > It depends on whether distros can be convinced to enable it by default, > and install by default any necessary userspace infrastructure. The > most important thing for field debugging is Just Knowing that you have > all the bits necessary to perform useful debugging without having to > find some RPM that matches the kernel that the machine is actually > running now, and not the one that was present when the machine was > installed. Which is precisely why dprintk() is such a bad choice as a basis for a set of trace points: every new patch and bugfix that the distro applies will result in a reshuffling of the trace points as code is cleaned up and moved around or removed entirely. Cheers Trond