JDWP Tools

• jdwp_lib contains a library to interact with a remote JVM via JDWP.
• jdwp_stack_trace is a tool build with jdwp_lib to set breakpoints and print a stack trace to System.err when the breakpoint is hit.

When debugging latency sensitive processes it's important to have lightweight breakpoints but I found that IntelliJ's debugger needs MANY round trips (some of them are in parallel) to print a stack trace. This is because IntelliJ's debugger is walking the stack and asking the JVM information about each stack frame which requires O(n) round trips where n = stack depth.

jdwp_stack_trace tool relies on Thread.dumpStack to print a stack trace to System.err. The first breakpoint will require 3 round trips (look up dumpStack method ID, invoke method, resume VM), but subsequent breakpoints only need 2 round trips.

Run

# Get rustup from your package manager or use www.rust-lang.org/tools/install
$ rustup default nightly
$ cargo build
$ ./target/debug/jdwp_stack_trace