Re: [RFC][PATCH] Add a flight data recorder for scsi commands

["Jörn Engel" <joern@logfs.org>]

On Tue, 27 August 2013 19:54:22 -0400, Steven Rostedt wrote:
> On Tue, 27 Aug 2013 18:03:25 -0400
> Jörn Engel <joern@logfs.org> wrote:
> 
> > Here is a fun patch in an early state.  Essentially I want to trace
> > scsi commands, which has already been done long ago.  The problem I
> > have is that I care about all the scsi commands for one particular
> > device - without knowing in advance which device it will be.  Once I
> > know the device in question, I want to dump the last X commands.
> 
> Is the device passed to the trace point? If so, you can add a filter on
> that device. You can even create a separate buffer to just trace that
> device.

"without knowing in advance which device it will be"

I have to trace all devices, because I don't know the interesting one
ahead of time.  And after the fact, I only care about one device.  So
having per-device trace buffers seems to be The Right Approach(tm).

And having multiple trace buffers is where I cannot easily make my
problem fit your infrastructure.  

Jörn

--
If you're willing to restrict the flexibility of your approach,
you can almost always do something better.
-- John Carmack
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