linux-kernel - Re: [patch 0/5] activate & deactivate dprintks individually and severally

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Message-ID: <20090121152858.GA23953@redhat.com>
Date:	Wed, 21 Jan 2009 10:28:58 -0500
From:	Jason Baron <jbaron@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Linux NFS ML <linux-nfs@...r.kernel.org>,
	Linux NFSv4 ML <nfsv4@...ux-nfs.org>,
	SystemTAP ML <systemtap@...rces.redhat.com>, gnb@....com
Subject: Re: [patch 0/5] activate & deactivate dprintks individually and
	severally

On Tue, Jan 20, 2009 at 12:29:30PM +1100, Greg Banks wrote:
> 
> As mentioned in the recent discussion on NFS trace points on the NFS &
> SystemTap mailing lists.  This patch allows field support staff and
> kernel developers debug kernel problems, by enabling them to treat
> dprintks as precise trace points rather than syslog spamming tools.
> 
> This is a forward ported (from 2.6.16), updated, and split version
> of a patch that has been used in SGI's internal development tree for
> the last few months.  The very first version of this was used about
> eighteen months ago when debugging NFS/RDMA, which has an enormous
> number of dprintks and no other way to debug it.
> 
> Jason Baron suggested I post it here for review and contrast with
> his dynamic dprintk feature.
> 

yes, these two patch sets are very similar in the problem that they are
addressing. For me, one of the core differences, is that 'dprintk' has
per-debug statement control, while my solution, 'dynamic debug' has a
more per-module focused control. 'dprintk' thus checks a different
variable per-debug line to see if its enabled. On the other hand
'dynamic debug' can check 1 global variable (in the most common cases),
to see if its enabled or not. I think we can layer per-line check on top
of the 1 global variable check and have a more efficient solution that
still allows for fine-grained debugging.

'dprintk' also has a richer user interface, which allows for file, line,
module, and statement control. 

Thus, I think Greg and I can work together and combine the best features
of both patches. We will re-post a combined solution.

thanks,

-Jason
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