Profile-guided Optimizations

GraalVM Enterprise allows to apply a profile-guided optimizations (PGO) feature for additional performance gain and higher throughput of native images. With PGO you can collect the profiling data in advance and then feed it to the native-image builder, which will use this information to optimize the performance of the resulting binary.

One approach is to mitigate the missing just-in-time (JIT) optimization – to gather the execution profiles at one run and then use them to optimize subsequent compilation(s). In other words, you create a native image with the --pgo-instrument option to collect the profile information. The --pgo-instrument builds an instrumented native image with profile-guided optimization data collected of AOT compiled code in the default.iprof file, if nothing else is specified. Then you run an example program, saving the result in default.iprof. Finally, you create a second native image with --pgo profile.iprof flag that should be significantly faster.

Another approach is to collect profiles while running your application in JIT mode and then use this information to generate a highly-optimized native binary. This maximizes the performance even more.

Run a java program in JIT mode with a -Dgraal.PGOInstrument flag to gather the profiling information:
```
java -Dgraal.PGOInstrument=myclass.iprof MyClass
```
Use the collected data to generate a native image:
```
native-image --pgo=myclass.iprof MyClass
```
Run the resulting binary:
```
./myclass
```