For a few months now, it's been possible to get profiles from subprocesses (namely, the content process and plugin processes), although it's been somewhat touchy. Retrieving the profile was a synchronous operation that would deadlock if the subprocess was also waiting on a synchronous message from the parent. With bug 1116188 fixed, we gather profiles asynchronously, so this should, in theory, be far more reliable. We've been using the Gecko Profiler Add-on to read these profiles, but it'd be great if we could use the Browser Toolbox performance tool to examine these profiles from subprocesses as well. Here's an example of a profile from multiple processes: http://people.mozilla.org/~bgirard/cleopatra/#report=65e1e7573378b5918197efa9dc0ba4cbc3571351 Lining up the profiles horizontally like this all at the same time is excellent, as it allows us to get a sense of what was occurring in all processes for a given time slice. For example, for diagnosing slow tab switching, we would add markers in the parent for when the tab is being switched, and then look at the samples in the content process between those markers. It's fantastically useful. It's not critical - for not, we can continue to use the Gecko Profiler Add-on, but vporof suggested I file this bug so that we can dogfood the Browser Toolbox more. Getting multi-process support would really help us do that.
Triaging. Filter on ADRENOCORTICOTROPIC (yes).
Priority: -- → P3
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