Debugging and Tuning

Friday last week I had a major break-through: I saw the shell again after more than four weeks. Debugging was exactly as much fun as everybody says it is. It's particular frustrating if you spend five hours from not having any clue what part of the system might be causing a crash over narrowing it down to a small number of hypotheses to finding a really stupid mistake that you can't believe you are responsible for. Gdb is a close friend now.

For testing the interpreter I was basically using the startup procedure. When the interpreter starts up it reads in and parses a bunch of source files with definitions. So there surely are a couple of more bugs that this "test" did not expose. Before I try running other programs to tease out more bugs, though, I will spend a little more time on performance tuning. Having to wait a minute or two until the interpreter got to a point where it broke while parsing the standard files was an annoyance while debugging last week (and besides, that performance is unacceptable).

Three items are on my performance tuning to-do list for now:

• Do some profiling and try to speed up the hot spots in the MM code
  
• Implement asynchronous collect (so far there's only synchronous)
• Implement a smarter collection trigger policy