mfs and buildworlds on da SunFire x4600

[Kris Kennaway]

On Thu, May 03, 2007 at 02:39:55AM +0800, Mars G. Miro wrote:
> Greetz,
> 
>    I got my hands on a SunFire x4600. This is a dual-core 8-way
> Opteron (dmesg shows 16 CPUs) w/c has 32G RAM. FreeBSD 6.2/amd64 runs
> fine on it despite:
> - 'reboot' doesnt work, machine just hangs in there.

There is a sysctl to specify an alternate reboot method.

> - front USB ports wont work for a USB keyboard, just use da ports at da 
> back.
> 
>   I've read a lot of threads in da past (and da BSDCan 2006 paper)
> regarding mfs on /usr/src and /usr/obj to speed up buildworlds,
> unfortunately it doesnt seem to improve things. I've tried both a
> malloc and swap based async non-softupdates mfs (and rebooted da box
> every after) but my buildworld speeds seem to be just da same as I do
> it on da MPT SAS disk w/c is just around ~18mins.

It is probably a combination of issues:

1) There is still some disk access because of accessing things like
binaries in /usr.  This will hurt more for parallel builds because
your disk hardware is single-threaded, so I/O delays will serialize
you.  If you really wanted you could compare to a build in a md-hosted
chroot to completely eliminate the disk, but this is just a game.

2) Buildworld doesn't parallelize well to 16 CPUs.  Large parts of it
are completely non-parallel.  This is probably your main problem.

You definitely should be measuring some difference - you need to use
time(1) though instead of just estimating.

Kris