[HEADSDOWN] swap_pager.c calming down...

[Poul-Henning Kamp]

I'm through with my first level of changes to swap_pager.c and the
results are better than even I had hoped.

The new per-device round-robin allocation performs a tad _better_
than the old striping when it comes to distribution of I/O requests
over multiple devices, given that there now is no upper limit on
the number of swap devices, this is a clear win-win.

For systems with less than the (previously) hardconfigured NSWAPDEV
limit, kernel malloc usage is lower, now we only allocate that space
which we need.

The next level of changes will be to go directly to GEOM for disk
devices, rather than take the detour over vnodes and specfs.
This will not happen in the first couple of weeks I suspect.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.