Performance comparison, ULE vs 4BSD and AMD64 vs i386

Jem Matzan jem at
Tue Feb 24 13:39:36 PST 2004

I've spent the last two weeks benchmarking an AMD64 machine with
FreeBSD. I've acquired a decent amount of data that seems to show
conclusively that a kernel using the ULE scheduler has slower compile
times and inferior performance to a kernel running the 4BSD scheduler.
The difference is roughly 11% in some cases, although I have not yet run
all of the numbers through ministat yet. This is consistent for both
i386 and AMD64.

I tried both 5.2-RELEASE and 5.2.1-RC2 and the performance results were
identical for this system.

I've also found that the AMD64 edition of FreeBSD is significantly
slower than the i386 edition when doing a buildworld (with any amount of
simultaneous makes), but ubench reports a slightly higher CPU score. I'm
still trying to work with John McCalpin to get Stream to work properly
for testing, and I have openssl speed tests that I have not yet

For testing I used the same make.conf and rc.conf for both systems and
eliminated every possible option from the kernel that I could, without
breaking anything. I ran all tests in single user mode with none of the
usual background process (network, usbd, fsck, etc.) running. The kernel
config files were as identical as they could possibly be.

I collected three sets of data per run, each being performed immediately
after a fresh restart, and for the buildworld tests I did three sets of
those three sets, for a total of nine per scheduler.

I'm willing to type in all of my data on a temporary page before I
finish testing everything (I have another system to test before the
review can be written) for the purpose of peer review, but I don't want
to go to the trouble if no one here has a reason to dispute my findings.
I thought that ULE was supposed to offer superior performance -- or at
least, that's the word around the Internet -- but I have yet to discover
that through my experience. Can anyone offer any possible explanation
for ULE performing worse than 4BSD? How about AMD64 being slower than
i386 on the same hardware? By slower, I mean a buildworld -j4 took about
400 seconds longer in AMD64 mode.


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