Hyperthreading network benchmark

[kuas <ku4s@users.sourceforge.net>]

Hi all,

I found enabling hyperthreading for Xen (the hypervisor layer) would 
degrade network performance. I wonder if the synchronization cost of Xen 
(the hypervisor) running on multi cores/multiprocessors environment is 
high (around 30 %). The benchmark I did is against Intel Pentium 2.4 MHz 
Hyperthreaded CPU and Gigabit network (ethernet and switch). I was using 
WebStone 2.5 benchmark against Apache 2.0.50-1.0 (FC1 httpd package).  I 
was also running 2.4.27 for the domains kernel. The result I have:
1. Native:
    a. Hyperthread enabled: 370 Mb/sec
    b. Hyperthread disabled: 270-290 Mb/sec
2. Domain 0 has the same performance around: 270 Mb/sec
3. Domain 1:
    a, Hyperthreaded enabled, domain1 run on different core: 175-185 Mb/sec
    b. Hyperthreaded disabled or even if enabled domain 1 is forced to 
be in the same Core with domain 0: 255-265 Mb/sec

Please note, I was only sending request to one domain at a time. It 
seems when the two domain ran in the same core we had higher 
performance. I wonder if any other people has done almost similar test 
and have similiar/opposite behavior. Are these behaviors make sense?

Thanks in advance for any comments.

Kuas.




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