Subject: Multiple Tracers
From: Steven Whitehouse <swhiteho@redhat.com>
To: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, axboe@kernel.dk
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Organization: Red Hat UK Ltd
Date: Wed, 08 Apr 2009 14:35:03 +0100
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

A little while back I posted a RFC patch which added gfs2 glock tracing
to blktrace. There was a suggestion that I should look instead at the
generic tracing code and add a new tracer, but I've come up with a
couple of issues along the way.

I think from what I can see that its only possible to run a single
tracer at once, so running blktrace (for example) would preclude me from
also tracing gfs2's glocks at the same time. Also, I can see no
mechanism by which I could ensure the sequencing between the blktrace
and glock traces other than exporting the blktrace sequence number, even
if running multiple tracers at the same time was possible.

Is there a solution to this which I've not spotted, or would something
along the lines of my previous patch[*] be a reasonable solution at this
stage?

Steve.

[*] http://markmail.org/message/ujkd6bre2td27pfb


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