> I'm working with a dual xeon platform with 4 dual e1000 cards on different
> pci-x buses. I'm having trouble getting better performance with the second
> cpu enabled (ht disabled). With a UP kernel (redhat's 2.4.18), I can route
> about 2.9 gigabits/s at around 90% cpu utilization. With a SMP kernel
> (redhat's 2.4.18), I can route about 2.8 gigabits/s with both cpus at
> around 90% utilization. This suggests to me that the network code is
> serialized. I would expect one of two things from my understanding of the
> 2.4.x networking improvements (softirqs allowing execution on more than
> one cpu):
The Fujitsu guys have a nice summary of this:
http://www.labs.fujitsu.com/en/techinfo/linux/lse-0211/index.html
Skip forward to page 8.
Dont blame the networking code just yet :) Notice how worse UP vs SMP
performance is on the P4 compared to the P3?
This brings up another point, is a single CPU with hyperthreading worth
it? As Rusty will tell you, you need to compare it with a UP kernel
since it avoids all the locking overhead. I suspect for a lot of cases
HT will be a loss (imagine your case, comparing UP and one CPU HT)
Anton
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This archive was generated by hypermail 2b29 : Tue Jan 07 2003 - 22:00:24 EST