> When using the Linux "perf" tool to do system profiling, symbol names of > running Java methods cannot be decoded, resulting in unhelpful output > such as: > > 10.52% [JIT] tid 236748 [.] 0x00007f6fdb75d223 > > Perf can read a simple text file format describing the mapping between > address ranges and symbol names for a particular process [1]. > > It's possible to generate this already for Java processes using a JVMTI > plugin such as perf-map-agent [2]. However this requires compiling > third-party code and then loading the agent into your Java process. It > would be more convenient if Hotspot could write this file directly using > a diagnostic command. The information required is almost identical to > that of the existing Compiler.codelist command. > > This patch adds a Compiler.perfmap diagnostic command on Linux only. To > use, first run "jcmd <pid> Compiler.perfmap" and then "perf top" or > "perf record" and the report should show decoded Java symbol names for > that process. > > As this just writes a snapshot of the code cache when the command is > run, it will become stale if methods are compiled later or unloaded. > However this shouldn't be a big problem in practice if the map file is > generated after the application has warmed up. > > [1] > https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt > [2] https://github.com/jvm-profiling-tools/perf-map-agent
Nick Gasson has updated the pull request incrementally with one additional commit since the last revision: Make DumpPerfMapAtExit a diagnostic option ------------- Changes: - all: https://git.openjdk.java.net/jdk/pull/760/files - new: https://git.openjdk.java.net/jdk/pull/760/files/959adca5..d8a399a1 Webrevs: - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=760&range=04 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=760&range=03-04 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/760.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/760/head:pull/760 PR: https://git.openjdk.java.net/jdk/pull/760
