Date: Tue, 22 Dec 2009 17:13:53 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: Jason Baron <jbaron@redhat.com>
Cc: mingo@elte.hu, rostedt@goodmis.org, fweisbec@gmail.com,
       linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] dynamic debug - adding ring buffer storage support
Message-ID: <20091222161353.GB20225@jolsa.lab.eng.brq.redhat.com>
References: <1261481526-17630-1-git-send-email-jolsa@redhat.com>
 <20091222153955.GD3308@redhat.com>
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On Tue, Dec 22, 2009 at 10:39:56AM -0500, Jason Baron wrote:
> On Tue, Dec 22, 2009 at 12:32:06PM +0100, Jiri Olsa wrote:
> > Hi,
> > 
> > as I use dynamic debug sometimes, I thought it could be useful having
> > the possibility to store the output somewhere else than dmesg.
> > 
> > The attached patch implements support for storing dynamic debug
> > messages to the ring buffer.
> > 
> > The dynamic debug allows simple addition of new flags,
> > so I added 'r' flag for ring buffer storage.
> > 
> > I used the ring buffer implementation from trace framework.
> > 
> > hopefuly this could be any use for others as well...
> > plz let me know what you think,
> > 
> > jirka
> > 
> 
> hi,
> 
> I like the idea of using the ring buffer for output. However, I'm not
> sure why we need a separate one for this. I like adding the 'r' for ring
> buffer storage, by why not just make this path call 'trace_printk()', and
> store the string in the existing kernel tracing ring buffer? That way it
> can interleave with other trace data as well.

that way you need to enable tracing as well... but thats ok I guess :)

I was investigating trace events for this, but did not find a way
to put variable length argument inside... and I overlooked the
trace_printk, I'll look on it and see how it fits, thanks

also having separate ring buffer makes the 'trace'/'trace_pipe' code
really simple (suprissingly) compared to ftrace, and I thought
on this place it could last for some time.. ;)

jirka

> 
> thanks,
> 
> -Jason
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