- Update to latest version of vscode-ghc-simple (0.1.19 at time of writing)
- (The following two steps makes diagnosis easier, if you can reproduce the
  problem in some other way, no problem, please also tell me.)
- Reproduce the issue in no more than one workspace root.
- Close all Haskell document tabs
- Check if there are more than expected `ghci` processes: If it was a
  stack/cabal project, and there were >= 2 ghc processes; or if it was just
  single files, and there are ghc processes remaining(*) -> Please open new
  issue with log and ideally but not necessarily minimal steps to reproduces
- Otherwise, no extra processes but memory usage is abnormal -> Probably just
  problem with GHC. I don't think I can do much, but please reply under
  https://github.com/dramforever/vscode-ghc-simple/issues/56

(*) Update: VSCode caches files under the hood, and there's no way to
programatically get the open editors. As such you may see processes
corresponding to cached files. To confirm that these aren't rogue, re-open the
files and the number of GHCi processes should not increase.

Technical details: It due to a misunderstanding of the Node `child_process.exec`
API. I think the extension, when the output buffer is exceeded, assumes that the
error means `ghci` has died when it's still running, which leaves rogue `ghci`
processes behind, consuming large amount of system resources.