Messages in this thread | | | Date | Sat, 4 Jan 2003 14:33:45 +1100 | From | Anton Blanchard <> | Subject | Re: Gigabit/SMP performance problem |
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> 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)
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