The swamp-pit that is the Linux memory manager (2.4.18 version)
There are a lot of documented knobs, valves, and levers that you can tweak to set the behavior of what calls itself a memory manager in various versions of 2.4. Unfortunately, the version of Linux we're stuck with at work is one of the transitional versions where the core team (no longer just Linus) ripped one broken memory manager out and replaced it with another broken memory manager, so we've got a version of the memory manager that's can't handle a busy (8000+ processes, 8gigabytes, 4x 3ghz Xeon) machine and which doesn't have any documented -- even in the kernel source and documents -- ways to correct the spiffy way it sandbags when the machine gets down to 15.8gigabytes of swap. So I'm tweaking values by hand, and trying to guess about which goddamn magic setting (which will be obsolete as soon as we migrate to the next dot-release of the linux kernel) will convince the system to start writing out dirty pages before we get 5 minutes behind.
Aaaaarrrrgggghhh!
I say again; Aaaaarrrrgggghhhh!