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FreeBSD s/390 Port in the works
brad-x writes: "It appears that an enterprising gentleman has taken the time to port FreeBSD to the s/390. It needs some work yet, as his project page suggests, but if he makes it happen it will definitely be very cool. Check it out!"
5.0-CURRENT includes SMPng which is supposed to improve MP performance dramatically by knocking away that single giant lock. I have heard people running FreeBSD on a quad Intel processor setup a while ago on freebsd-questions... though I'm not sure how well performance would scale compared to a dual processor setup of the same processor speed.
I haven't been able to fully parse the boot log, so I'm not sure if it is utilizing more than one processor or not, but the thing that the write-up forgot to mention was that it was tested under the S/390 emulator (aka Hercules). I'm not sure what Hercules is and how it work per se... but it's still a huge jump forward for FreeBSD.
It isn't really a 2CPU limitation per-sey. The problem is performance has diminishing returns as you go past 2 cpus. Giant kernel lock means that one cpu has access to the memory space at a time and this is why performance can't scale well with this design.
The good news is that it works remarkably well on 1 or 2 cpu systems. It beat the performance of Linux 2.2 kernels and still gives 2.4 kernels a run for their money in most situations. When you start running mores cpus then performance will only go up a little bit so it really isn't worth it at that point.
FreeBSD 5.0 will not have this limitation and will scale nicely. I'm just not sure how far it will go at first but you can be sure that it will improve from there now that a decent setup for SMP is in place now (with 5.0).
Intrestingly enough NetBSD does not run on the 390.
There is a FreeBSD port of the emulator in /usr/ports/emulators/hercules; if you're running another BSD flavor and it doesn't have this port you'll likely have an easy time importing it.
// -- http://www.BRAD-X.com/ --
FreeBSD SMP has always supported more than 2 CPUs. While FreeBSD 5.0 Developers Prerelease with SMPng might be more efficient, FreeBSD 4.6-RELEASE will boot today on a quad CPU x86 system. It will also boot on octal x86 CPU moterboard, with some hacking. Unfortunately, octal CPU x86 motherboards chipsets are rather different. These the mailing list archives for the details.