performance_notes.txt

-------------------------------------------------------------
                A selection of performance notes.
-------------------------------------------------------------

-------------------------------------------------------------
                Async-Profiler
-------------------------------------------------------------

Install async profiler;

```
inventory install async_profiler
```

Make sure you have added following JVM settings:
```
-XX:+UnlockDiagnosticVMOptions
-XX:+DebugNonSafepoints
```

And to run, execute the following (s
```
profiler.sh collect -d 60 --jfrsync  ${JAVA_HOME}/lib/jfr/default.jfc  -f profile.jfr Worker
```

-------------------------------------------------------------
                Perf
-------------------------------------------------------------

Make sure you have added 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
```