performance_notes.md

A selection of performance notes

This document contains some useful performance notes.

Async-Profiler

Install async profiler:

inventory install async_profiler

Make sure you have added the following JVM settings:

-XX:+UnlockDiagnosticVMOptions
-XX:+DebugNonSafepoints

And to run, execute the following if you want a JFR file which can be analyzed with Java Mission Control:

asprof collect -d 60 --jfrsync  ${JAVA_HOME}/lib/jfr/default.jfc  -f profile.jfr Worker

Use the following for more accurate profiling:

asprof collect -d 60 --jfrsync  ${JAVA_HOME}/lib/jfr/default.jfc  -e cycles --cstack lbr  -f profile.jfr Worker

Or use the following if you do not care for a jfr file but want a flamegraph directly:

asprof collect -d 60 -f flamegraph.html Worker

Perf

Make sure you have added the following JVM settings:

-XX:+UnlockDiagnosticVMOptions
-XX:+DebugNonSafepoints
-XX:+PreserveFramePointer

Creating a perfmap with Java 17+:

jcmd <pid> Compiler.perfmap

https://www.doof.me.uk/2021/02/28/generating-perf-maps-with-openjdk-17/

JFR

-XX:+UnlockDiagnosticVMOptions
-XX:+DebugNonSafepoints
-XX:+PreserveFramePointer
-XX:+FlightRecorder
-XX:StartFlightRecording=duration=3600s,filename=recording.jfr

Page Cache

Clear pagecache only:

sync
echo 1 | sudo tee /proc/sys/vm/drop_caches

Clear dentries and inodes:

sync
echo 2 | sudo tee /proc/sys/vm/drop_caches

Clear pagecache, dentries, and inodes:

sync
echo 3 | sudo tee /proc/sys/vm/drop_caches