Re: [ltt-dev] Fw: [PATCH] ext4: Add markers for better debuggability

[Theodore Tso <tytso@mit.edu>]

On Fri, Jan 09, 2009 at 09:49:01AM -0500, Mathieu Desnoyers wrote:
> 
> Given this is meant to be in the mainline kernel, using tracepoints
> rather than markers would be more appropriate. Please see
> Documentation/tracepoints.txt and samples/tracepoints/ for details.

I saw that, but I'm still not sure how I would actually *use*
tracepoints.  I can use markers today with Systemtap, and I need an
easy way to be able to selectively do things like "trap and print all
of the logged data when the ext4_request_inode tracepoint/marker is
tripped where dev=='dm-8'".

Unfortunately, Systemtap seems doomed given its current course and
direction, so I'm not opposed to moving to another solution --- I just
need a HOWTO that demonstrates how I can do this painlessly and
easily; preferably without having me have to manually hack up a kernel
module each time I want to implement the tracing

Is there an easy way to do that using ltt today?  Can you point me at
a sample of how this could be done?

						- Ted