> > Given that any time that happens we end up caring much less about
CPU
> > usage and much more about disk IO, for any of these cases that use
> > non-random access, compressing the data before sending it to disk
would
> > potentially be a sizeable win.
>
> Note however that what the code thinks is a spill to disk and what
> actually involves disk I/O are two different things. If you think
> of it as a spill to kernel disk cache then the attraction is a lot
> weaker...
Yes, that is very true. However it would also increase the probability
that spill to disk is not needed, since more data fits in RAM.
It would probably need some sort of plugin architecture, since the
fastest compression algorithms (LZO) that also reach good ratios are
gpl.
LZO is proven to increase physical IO write speed with low CPU overhead.
Andreas