There are countless ways to talk about performance, so let's start with one simple case that is both relevant for our daily usage and displays terrible performance: gcc and clang on minix.

• Clang is significantly slower than gcc on minix, and it's supposed to be faster.
• There is high idle time when gcc and clang are executing, suggesting high i/o wait time

(Timing measurements to be done.)

• Run with huge primary cache: no more idle time. clang is still significantly slower than gcc though, and gcc still isn't very fast.
• Run with /usr/tmp, /tmp and /usr/src on ramdisks: almost no idle time any more.
• Marking unreferenced blocks as clean if they're dirty: happens but doesn't help much in real time.
• Defer evicting dirty blocks from the cache, prefering a clean block even if it's older in order to batch write operations: helps with reducing flushall() calls but not much in real time.