Recently I checked Profile-Guided Optimization (PGO) improvements on multiple projects. The results are here. E.g. PGO helps with optimizing Envoyproxy. PGO results for other proxies like HAProxy you can be found in the repo above. According to the multiple tests, PGO can help with improving performance in many other cases. Since there are already some performance-oriented requests like #251 - I think trying to apply PGO to the VTS module can be a good thing.

I can suggest the following action points:

• Perform PGO benchmarks on VTS. If it shows improvements - add a note to the documentation about possible improvements in VTS performance with PGO.
• Providing an easier way (e.g. a build option) to build scripts with PGO can be helpful for the end-users and maintainers since they will be able to optimize VTS according to their workloads

Maybe testing Post-Link Optimization techniques (like LLVM BOLT) would be interesting too (Clang and Rustc already use BOLT as an addition to PGO) but I recommend starting from the usual PGO.

Here are some examples of how PGO optimization is integrated in other projects:

• Rustc: a CI script for the multi-stage build
• GCC:
  • Official docs, section "Building with profile feedback" (even AutoFDO build is supported)
  • A part in a "wonderful" configure script
• Clang: Docs
• Python:
  • CPython: README
  • Pyston: README
• Go: Bash script
• V8: Bazel flag
• ChakraCore: Scripts
• Chromium: Script
• Firefox: Docs
  • Thunderbird has PGO support too
• PHP - Makefile command and old Centminmod scripts
• MySQL: CMake script
• YugabyteDB: GitHub commit
• FoundationDB: Script
• Zstd: Makefile
• Foot: Scripts
• Windows Terminal: GitHub PR
• Pydantic-core: GitHub PR
• file.d: GitHub PR
• OceanBase: CMake flag