Roadmap of potential features and fixes #2

Some of the things I have planned:

• UX
  • Better error handling (e.g. when providing a wrong syscall tracepoint name, we don't handle that nicely and the UX is bad) (2abb8c0)
  • Allow running tests and whatnot with cargo (7c14cd0)
  • Add info subcommand to show environmental details that might affect rbperf to aid debugging (e81748a)
• Quality
  • Add tests for C data structure parsing and "serialisation". Run valgrind / asan on them, too (2e3d1c0)
  • Compile BPF code with warnings on (cb0e7b4)
  • Gather error statistics (right now they are mixed / not well categorised, e.g. a map can fail to write in kernel or to read from in userspace) (4de5dee)
  • Upstream elfutils and zlib static linking patches (libbpf/libbpf-sys@371a85d, libbpf/libbpf-rs@5bed52a)
  • Add tests for big stacks that require BPF tail-calls (b474d3f)
  • Address PID reuse race condition: ( 272c8f3)
  • Verify that frames that we think are native are indeed native frames (https://github.com/javierhonduco/rbperf/blob/422c5ca6ffd0d7693/src/bpf/rbperf.bpf.c#L235)
• BPF
  • Logging is enabled by default in the BPF program. This has high overhead and it is not needed most of the time (422c5ca)
  • Evaluate using ring buffers
    • Add it as opt-in (8a1e048)
    • Run some tests to see how it behaviour compares to perf buffers
• Docs
  • Add a document on architecture, as well as in-depth comments in the BPF code
  • How to debug issues
  • How to add support for Ruby versions

• New features
  • Binary disk format
  • More output formats (folded stacks, chrome tracing, raw?)
  • Ensure it works in arm64
  • C function tracing, both from cruby or the libraries it dynamically links to (uprobes)

• Experimental ideas
  • Allocation tracing (w/ mem leak detection)
  • Request-specific data

• Other
  • Ensure we work with YJIT (asked in https://github.com/Shopify/yjit/. It works so far, but this might change)
  • Add git revision to the future info subcommand and in the BPF's metadata section

• Release
  • Publish x86_64 binaries

Simplify execution context fetching:

(gdb) p/x ruby_current_vm_ptr->ractor->main_thread->ec
$1 = 0x20729b0
(gdb) p/x ruby_current_ec
$2 = 0x20729b0