iostat improvement

[mlelstv%serpens.de@localhost (Michael van Elst)]

NetBSD's iostat provides only a small number of measurements showing
the rate and volume of I/O requests and a measurement for the time
a disk is busy doing I/O. This is not sufficient for disk systems
that allow some amount of parallelism in handling I/O requests
as disk systems can have a busy time of 100% while still not saturated.

I've added code to measure I/O service times and concurrency for
the kernel bufq and for the disk itself. This measured values are
similar to what Solaris and Linux collect.

A patch to -current can be found at

http://ftp.netbsd.org/pub/NetBSD/misc/mlelstv/iostat.diff

I plan to commit this in the near future but comments are of course welcome.


-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."