Tune Envoy by PGO

Envoy Deployment Tuning by PGO

PGO (Profile-Guided Optimization) allows your compiler to better optimize code for runtime performance. Applying PGO to Envoy can result in a 10% enhancement in performance.

Use the information below as general guidance on how to tune Envoy by PGO.

LLVM/Clang build

When you build Envoy using Bazel and LLVM/Clang, you should use the latest compiler version. For optimal results, it is advisable to build Bazel from the most recent source code . Refer to the LLVM Documentation and Clang Documentation for specific build details.

Overview of building Envoy with PGO

Here is an overview of the steps that you will need to take to build Envoy with PGO:

• Make sure you have LLVM, Clang, and compiler-rt installed locally
• Build Envoy using Clang, but with instrumentation
• Use the instrumented Envoy to generate profiles, which consists of two steps:
  • Running the instrumented Envoy on tasks that represent how users will use it
  • Using a tool to convert the raw profiles generated from the previous step into a single, final PGO profile
• Build a final release Envoy using the profile collected from your benchmark

Detailed steps on how to build Envoy with PGO

Follow and run the steps below:

1. Build Envoy with instrumentation:

    

        
        
            bazel build -c opt --copt="-fprofile-generate=/path/to/stage2/profiles" --cxxopt="-fprofile-generate=/path/to/stage2/profiles" --linkopt="-fprofile-generate=/path/to/stage2/profiles"  envoy --jobs=$(nproc)
        
    

2. Generate the profiles:

Run the Envoy built in step 1 with your target test cases. When the test has finished, run the following command to kill the Envoy services:

    

        
        
            sudo pkill -2 envoy
        
    

You should now have a few *.profraw files in /path/to/stage2/profiles/. You need to merge these using llvm-profdata, even if you only have one file. The profile merge transforms profraw into actual profile data. This can be done with the following command:

    

        
        
            /path/to/clang/llvm-profdata merge -output=/path/to/output/profdata.prof /path/to/stage2/profiles/*.profraw.
        
    

3.Build a final Envoy release

Now, build your final, PGO-optimized Envoy.

Run the following command:

    

        
        
            bazel build -c opt --copt="-fprofile-use=/path/to/output/profdata.prof" --cxxopt="-fprofile-use=/path/to/output/profdata.prof" --linkopt="-fprofile-use=/path/to/output/profdata.prof" envoy.stripped --jobs=$(nproc) 
        
    

LLVM/Clang PGO Documentation

You can view more options for LLVM/Clang PGO in the profile-guided-optimization documentation.