Evaluate using Profile-Guided Optimization (PGO)

[zamazan4ik]

Hi. Thanks for the project!

Profile-Guided Optimization (PGO) is a compiler optimization that allows to use of runtime statistics for performing better compiler optimizations. I applied PGO to different software in different domains (including operating systems like Linux kernel) - all the results are available at https://github.com/zamazan4ik/awesome-pgo . Since there are multiple claims that PGO helps operating systems like Linux and Windows, I think trying to evaluate PGO effects for rt-thread can be a valuable work since (according to the README) the project aims to provide high performance.

I can suggest the following action points:

• Perform benchmarks with PGO for rt-thread If it shows some positive effects - add a note to the documentation about PGO
• Integrate building rt-thread with PGO into the build scripts
• Optimize prebuilt binaries with PGO (if any) if it's possible to gather a representative enough training workload.

Some results about PGO efficiency for operating systems:

• Linux kernel:
  • Paper
  • Microsoft presentation
  • ASOS (Application Specific Operating System)
  • TCP Stream perf
  • Phoronix post
  • Yet another attempt to PGO Linux kernel: http://coolypf.com/kpgo.htm
  • Gentoo Wiki
  • Optimizing Linux kernel with Clang. An article(in Russian) and results
• Windows: 5-20% improvement according to the presentation

This issue is not a bug - it's just an idea of how the rt-thread's performance can be improved.