Importing from async‐profiler (Java)

The async-profiler tool can be used to profile Java applications and generate trace files that can be imported into speedscope. To do this install async-profiler from github. The easiest way to do this is to download a binary build of the latest release from the releases page and unzip it.

Once installed, a profile file can be created by using async-profiler's collapsed output format, which is specified via -o collapsed. For example:

1. Automatically profile for a fixed length of time

Find the pid or name of the process you want to profile using jps. Then run the following command to profile the process for s seconds:

./asprof collect -d <s> -o collapsed -f profile.collapsed <progname or pid>

2. Manually start and stop profiling

Find the pid or name of the process you want to profile using jps. Then run the following command when you want to start profiling:

./asprof start <progname or pid>

When you want to stop profiling, run:

./asprof stop -o collapsed -f profile.collapsed <progname or pid>

Once a properly formatted trace file exists, drop the resulting profile.collapsed into (https://www.speedscope.app/)

To view it offline, you'll need to install speedscope via npm:

npm install -g speedscope

Then you should be able to open it like so:

speedscope profile.collapsed