Re: collecting static data related to tracing

From: Steven Rostedt
Date: Wed May 19 2010 - 10:44:26 EST

On Wed, 2010-05-19 at 09:28 +0200, Frederic Weisbecker wrote:
> On Tue, May 18, 2010 at 04:45:09PM +0200, Johannes Berg wrote:

> This is a place where events injection might be suitable perhaps.
> Either kernel or user space event injection.
> kernel space injection would be a simple trace event declared that
> have a callback called when it gets enabled. This callback would
> inject any events it wants.
> userspace injection could be a bit different, the user can inject
> its own format and events content toward a debugfs or whatever file.
> This would be suitable if userspace have few things to inject,
> otherwise we would need to think about something else perhaps.

The userspace injection actually sounds like a good idea. I don't think
it needs to tell the kernel about it. Since it is running the trace.
Perhaps just have a way that the userspace can add its own events to the
recording file.

I guess this would be closer to what LTTng does with channels.

That is, you could have a separate recording stream to write events that
tell the tracer what is happening. It would be nice to have a way that
userspace can read the trace clock timer though.

-- Steve

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