File I/O with SMP on FreeBSD 4.11 slow

[Nikolai Schupbach]

Hello,

We have installed FreeBSD 4.11 with SMP enabled in our kernel on a dual Intel
Xeon 3.2 EMT64 server. We have found file operations like untaring the ports
tree, or copying directories with many files extremely slow. However if we
disable SMP support and run on a single CPU the performance is fast.

Using iostat the performance to untar ports tree is around 4Mb/sec with an SMP
kernel. Without SMP iostat reports around 50Mb/sec.

Is this normal for 4.11? We tired SMP on 5.4 and it did not suffer from this
problem, but we had to revert to 4.11 for other performance reasons.

Are we better off to run without SMP?

--Nikolai