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Re: [tracecompass-dev] Event requests precedence

Hi Geneviève,

This is indeed an interesting problem. Now that analyses each run in their separate thread, the order in which they will receive events is, as you say, more or less random.

We talked some time ago about implementing "priorities" for event requests, so that a component could be guaranteed to receive events before or after another one. Something similar to https://bugs.eclipse.org/bugs/show_bug.cgi?id=409424 , but for event requests instead of signals.

Nowadays, I have to wonder if something like this would even be required. Since we can now have dependencies between analysis modules, could we reuse this dependency chain to determine the order in which they should receive coalesced request events? Is this something that would even make sense in the first place? I think it would apply to your current case (the "experiment analysis" depends on the trace's analysis, so would receive its events after those), but would it be always like this?

Cheers,
Alexandre


On 10/31/2014 03:06 PM, Geneviève Bastien wrote:
Hello,

I would like some information on how the event request coalescing works as of now and how I could make the following use case work:

* I have an analysis for an experiment (let's call it the virtual machine analysis) that runs an event request on the experiment. * That analysis also depends on individual analysis from the traces of the experiment (concretely the LttngKernelAnalysisModule from each kernel trace). * When the experiment analysis module is executed, it also makes sure the LttngKernelAnalysisModule from each child trace is executed. * But when I handle an event in the experiment, I want to be sure that the LttngKernelAnalysisModules have run with this event before handling it in the experiment.

If I just let things run by themselves right now, the order of the requests is random so the event may or may not have been handled by the traces before it is by the experiment.

How would be the best way to solve this?

Thanks,
Geneviève



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