Evaluate using Profile-Guided Optimization (PGO) for Deno

[zamazan4ik]

Hi!

I found the article about efforts that the Deno team spent on optimizing one of its tools - the LSP server. Recently I checked Profile-Guided Optimization (PGO) improvements on multiple projects including LSP servers like Clangd and Rust-Analyzer. The results are available here. Since this, I think it will be a good idea to try to optimize the Deno ecosystem with PGO.

I can suggest the following things to do:

• Perform PGO benchmarks on various Deno tools. If it shows improvements - add a note about possible improvements to the documentation. Providing an easier way (e.g. a build option) to build scripts to build the project with PGO can be useful for the end-users and maintainers too.
• It will be a good idea to integrate building with PGO into your CI pipelines. In this case, users will get already PGO-optimized binaries from the project, based on some generic target workload.

For the Rust projects, I recommend trying to start with cargo-pgo - it makes it much easier to start with PGO. However, direct work with PGO via the corresponding Rustc flags is also an option.

Here you can find different materials about PGO: benchmarks in different software, examples of how PGO is already integrated with different projects, PGO support in multiple Rust compilers, and some PGO-related pieces of advice.

After PGO, I suggest evaluating the LLVM BOLT optimizer (aka Post-Link Optimizer) - it can give more aggressive optimizations even after PGO. However, starting with regular PGO will be easier to do.

I would be happy to answer all your questions about PGO!

P.S. I already found one closed PR about PGO. Seems like it's related to the V8 stuff. What is the current status of enabling PGO for the V8 dependency in Deno?