For the past few weeks I’ve been using a few new sysctl.conf settings, in the hopes that they’d affect system speed somehow. Personally I think these are so esoteric as to be unpredictable outside a few select machines, so take from them what you will.
Technically these are mostly power management settings, and so they generally don’t have any bearing on system speed. However, they all point at virtual memory, so in that sense they could (but probably won’t) affect swapping conditions or power settings on some hardware. And that, in turn, can sometimes affect system speed.
Either way, try them if you care. Here is an original thread from 2006 that provides some early information about vm.dirty_ratio and vm.dirty_background_ratio, and some of the others are mentioned in this howto about disk activity.
Once again, just to be clear, I don’t think they’ll give much of an improvement speedwise, but you never know.