Documenting profiling

Author: Mario Macias

docs/profiling.md

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+# Profiling guide
+
+1. Run the agent with the `PROFILE_PORT` variable set to e.g. 6060.
+   - If you are executing the agent from the Openshift NetObserv Operator, you can do it by
+     adding the following section to your `ebpf` spec:
+   ```yaml
+   apiVersion: flows.netobserv.io/v1alpha1
+   kind: FlowCollector
+   metadata:
+     name: cluster
+   spec:
+     ebpf:
+       env:
+         PROFILE_PORT: "6060"
+   ```
+
+2. If you are running OpenShift/Kubernetes, port-forward the pod that you want to profile.
+
+    ```
+    oc -n netobserv-privileged port-forward netobserv-ebpf-agent-4kt9d 6060
+    ```
+   
+3. Download the required profiles:
+
+   ```
+   curl -o <profile> http://localhost:6060/debug/pprof/<profile>
+   ```
+   
+   Where `<profile>` can be:
+
+* `allocs`: A sampling of all past memory allocations
+* `block`: Stack traces that led to blocking on synchronization primitives
+* `cmdline`: The command line invocation of the current program
+* `goroutine`: Stack traces of all current goroutines
+* `heap`: A sampling of memory allocations of live objects.
+  * You can specify the `gc` GET parameter to run GC before taking the heap sample.
+* `mutex`: Stack traces of holders of contended mutexes
+* `profile`: CPU profile.
+  * You can specify the `duration` in the seconds GET parameter.
+* `threadcreate`: Stack traces that led to the creation of new OS threads
+* `trace`: A trace of execution of the current program.
+  * You can specify the `duration` in the seconds GET parameter.
+
+Example:
+
+```
+curl "http://localhost:6060/debug/pprof/trace?duration=20" -o trace20s
+curl "http://localhost:6060/debug/pprof/profile?duration=20" -o profile20s
+curl "http://localhost:6060/debug/pprof/heap?gc" -o heap
+curl "http://localhost:6060/debug/pprof/allocs" -o allocs
+curl "http://localhost:6060/debug/pprof/goroutine" -o goroutine
+```
+
+4. Use `go tool pprof` to dig into the profiles (`go tool trace` for the `trace` profile)