Re: LTTng kernel integration roadmap, update

From: Lai Jiangshan
Date: Wed Dec 03 2008 - 22:52:38 EST

Mathieu Desnoyers wrote:

> - Marker ID management
> Background :
> The markers are currently used to identify the numerical event IDs
> associated with a named event as well as the event types (format
> string) associated with that event. Those two informations are kept in
> a table written in the metadata channel. A "channel" could be thought
> as being a set of per-cpu buffers, where information transits. This
> information would typically be related to a specific tracer. Note,
> however, that the information generated by a tracer should always be
> parseable generically and be transformable into text output by a
> simple parser, because we want to permit analysis across information
> logged by the various tracer.
> Action item :
> The current event IDs are global to the whole kernel. It would be
> beneficial to change their scope so they are per-channel instead,
> because we can then encode most events in the low-order bits of the
> event ID bits, therefore keeping events as small as possible.

Hi, Mathieu Desnoyers:

It also required by ASCII text output.

ASCII text output needs get name&fmt from eID, but In current code,
I cannot find a reliable way to get name&fmt from eID. And also,
in the kernel space, we must get name&fmt from eID as fast as possible
by reason of performance. So I cannot use metadata channel for it.

When "Add periodical subbuffer flush for streaming" and "Marker ID management"
will done?

Thanks, Lai.

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