Hi Mathieu, On 28 July 2011 05:06, Mathieu Desnoyers <[email protected]>wrote:
> Hi all, > > I'd like to get feedback on the new UST 2.0 tracepoint event API. > The code still needs to be debugged (it does not compile yet), but the > basic structure of the API is in place, and I'd like to get feedback on > this. > ... > Note: the print formatting information is actually metadata exported for > the trace viewer. It does not add information to each event in the > trace. ... The tracepoint.h header contains a lengthy comment describing the > TRACEPOINT_EVENT() API, along with a usage example: > > http://git.lttng.org/?p=ust.git;a=blob;f=include/ust/tracepoint.h > > The macros describing the types available within the TP_FIELDS macro are > described at the beginning of: > > > http://git.lttng.org/?p=ust.git;a=blob;f=include/ust/lttng-tracepoint-event.h > > This link appears to be broken...? The examples in the email didn't seem to mention floating point trace info - is that catered for? Its not so useful in the kernel, but for userspace tracing its much more likely to be needed I guess. Thoughts ? > In addition to the type information that the format string provides, it could also be very useful for a consumer tool to be able to tell the units of the trace data - bytes, kilobytes, milliseconds, nanoseconds, etc. Not sure I can think of a neat way to add that into the API though - perhaps extending the format string with optional type decorator? Might be a bit counter-intuitive/ugly. Other random thoughts that occur - I've seen some tracing systems that have a "trace caliper" concept, where the start (say, of a transaction) and the end can be linked ... would this be useful as an explicit part of the API, or is it something that could/should be built at a higher level? These other tracers also tend to do what they call "end-to-end" tracing, where a trace hierarchy can be built (using the caliper start/end concepts) - not sure how that would be added to the API, but just thought I'd throw it out there for your consideration anyway. HTH. cheers. -- Nathan
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