Re: [Xen-users] Re: Limit i/o capacitiy?

["Artem Y. Pervin" <ArtemPervin@xxxxxxxx>]

>> Is there any way to limit the network i/o capacity of virtual machine
>> somehow? Say, I want a domU with id 1 to consume at much 0.5 MB/s of
>> host's bandwidth. Is it possible?

> Network interfaces:

> vif = [' .. rate=500Kb/s ..']

> regards

> Johannes

I`ve conducted a number of tests with the rate parameter of vif to
investigate the effect this parameter does. I was expecting to see a
proportional increase in performance of benchmark with the increasing
of rate. But the experimental data shows different results.

I`ve used a web-application as a workload and httperf as a benchmarking
tool. There parameters of httperf were the following:
> ./httperf --hog --client=0/1 --server=192.168.10.9 --port=50180 
> --uri=index.cgi --rate=200 --send-buffer=4096 --recv-buffer=16384 
> --num-conns=1000 --num-calls=1

There key values of httperf's reports are:

rate: 20KB/s
test-duration 193.906 s
Request rate: 0.0 req/s (0.0 ms/req)
Net I/O: 0.0 KB/s 

rate: 21KB/s
test-duration 193.907 s
Request rate: 0.0 req/s (0.0 ms/req)
Net I/O: 0.0 KB/s 

rate: 22KB/s
test-duration 193.966 s
Request rate: 4.9 req/s (204.0 ms/req)
Net I/O: 15.8 KB/s (0.1*10^6 bps)

rate: 25KB/s
test-duration 193.966 s
Request rate: 4.9 req/s (203.3 ms/req)
Net I/O: 15.8 KB/s (0.1*10^6 bps)

rate: 100KB/s
test-duration 193.967 s
Request rate: 4.9 req/s (202.7 ms/req)
Net I/O: 15.9 KB/s 

The performance (request rate) is 0 for rates 20 and 21 KB/s.
The 22KB/s value gives normal results.
However they don't improve much with subsequent increases of rate.

Is this correct behavior? May be I have misunderstood something in the
way the rate parameter should be used? Or passed wrong parameters to
httperf?

Thanks in advance.


--
Artem Pervin


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