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by dbg_nsk
3044 days ago
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Right, but even a single instruction placed on every backward branch and at the epilogue of every method causes noticeable impact on the performance. This is especially important in highly optimized code and that's why optimizing compilers like HotSpot C2 (and JET as well) try to remove as many safepoints as possible. Sometimes it even causes troubles like in this case: https://bugs.openjdk.java.net/browse/JDK-5014723 Good point about inspecting thread's callstack. Indeed, with conservative GC we had a problem: many popular profilers were incompatible with JET because they inspect threads at safepoints and we had none. When we implemented the precise GC, this problem disappeared and it was an additional benefit for us. However, there are alternative ways to gather thread's callstack out of safepoint. We use them to avoid safepoint bias in our profiler. You can read more about it here: https://www.excelsiorjet.com/blog/articles/portable-profiler... ---- Thanks for kind words! I'm glad that you liked the post! |
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