jrudolph
commented
8 years ago The first question would be whether those JVM processes are running long enough to have sufficient code compiled at all. Otherwise, you'd just get a lot of opaque Interpreter frames.
The actual functionality would probably need the perf-map-agent library to be loaded at the start of each of the Java processes to capture all JIT compilation from the start of the program till the end. The problem then is that it is likely that the JVM discards some compiled methods and reuses the same memory for new methods. That means that over the run of a Java process, a memory address may map to different symbols changing over time. So, you will need a dynamic symbol mapping mechanism that associates timestamps from perf traces with timestamps from the JVM compilation events.
To get there we'd need:
- to resurrect the persistent mode for the agent
- to output load/unload events with a timestamp that can be correlated with timestamps collected with perf
- a custom symbol mapping step that doesn't rely on perf-tools and perf-
.map files but directly maps (timestamp, address) tuples to the correct symbol at that time
All of these would be interesting to implement but not a short-term goal for now.
craiig
libbkmz
Hi all, I'm trying to profile systems that consist of lots of java processes being started and stopped over time. Does anyone know of a way to ensure that I can get a symbol mapping of each java process that gets run on my system? Just running once won't capture these transient processes, so I'd ideally like something that automatically makes a symbol dump, maybe on process termination? Any thoughts would be appreciate.
Not sure if this is the right place to ask, feel free to point me somewhere else! Thanks a lot for this tool.