Update 3_agent.md

Author: pareenaverma

content/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/3_agent.md

@@ -8,31 +8,41 @@ layout: learningpathall
 ---
 
 ## Java Flame Graph Generation via Java agent and perf
-To profile a Java application with perf and ensure proper symbol resolution, you must include libperf-jvmti.so when launching the Java application.
-- libperf-jvmti.so is a JVM TI agent library enabling perf to resolve Java symbols, facilitating accurate profiling of Java applications.
-- A specialized shared library, libperf-jvmti.so bridges perf and the JVM, enabling proper translation of memory addresses to Java method names during profiling.
+To profile a Java application with perf and ensure proper symbol resolution, you must include `libperf-jvmti.so` when launching the Java application.
+- `libperf-jvmti.so` is a JVM TI agent library enabling perf to resolve Java symbols, facilitating accurate profiling of Java applications.
+- A specialized shared library, `libperf-jvmti.so` bridges perf and the JVM, enabling proper translation of memory addresses to Java method names during profiling.
 
-1. Find and add libperf-jvmti.so to Java option
+1. Find where `libperf-jvmti.so` is installed on your Arm-based Linux server: 
+```bash
+pushd /usr/lib
+find . -name libperf-jvmti.so`
+```
+The output will show the path of the library that you will then include in your Tomcat setup file:
 ```bash
 vi apache-tomcat-11.0.9/bin/catalina.sh
-# add JAVA_OPTS="$JAVA_OPTS -agentpath:/usr/lib/linux-tools-6.8.0-63/libperf-jvmti.so -XX:+PreserveFramePointer"
+```
+Add JAVA_OPTS="$JAVA_OPTS -agentpath:/usr/lib/linux-tools-6.8.0-63/libperf-jvmti.so -XX:+PreserveFramePointer" to `catalina.sh`. Make sure the path matches the location on your machine from the previous step.
+
+Now shutdown and restart Tomcat:
+```bash
 cd apache-tomcat-11.0.9/bin
 ./shutdown.sh
 ./startup.sh
 ```
 
-2. Use perf to profile Tomcat, and restart wrk if necessary
+2. Use perf to profile Tomcat, and restart wrk that running on your x86 instance if necessary:
 ```bash
 sudo perf record -g -k1 -p $(jps | awk /Bootstrap/'{print $1}') -- sleep 10
 ```
+This command will record the collected data in a file named `perf.data`
 
-3. Convert the collected perf.data file into a Java flame graph using FlameGraph
+3. Convert the collected `perf.data` into a Java flame graph using FlameGraph
 ```bash
 git clone https://github.com/brendangregg/FlameGraph.git
-export PATH=$PATH:/root/FlameGraph
+export PATH=$PATH:`pwd`/FlameGraph
 sudo perf inject -j -i perf.data | perf script | stackcollapse-perf.pl | flamegraph.pl &> profile.svg
 ```
 
-4. Launch profile.svg in a browser to analyse the profiling result
+4. You can now successfully launch `profile.svg` in a browser to analyse the profiling result
 
 ![example image alt-text#center](_images/lp-flamegraph-agent.png "Java Flame Graph via Java agent and perf")