RE: [Xen-devel] Reduce CPU Utilization make Network Perfromancebetter??

["Santos, Jose Renato G" <joserenato.santos@xxxxxx>]

Just adding a few comments to Mark's reply

>> -----Original Message-----
>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
>> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
>> Mark Williamson
>> Sent: Sunday, October 07, 2007 8:22 PM
>> To: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Cc: Brian Fang
>> Subject: Re: [Xen-devel] Reduce CPU Utilization make Network 
>> Perfromancebetter??
>> 
>> > I don't know if the guess condition is wright.
>> > But I still not figure out how the improvement benefit 
>> network throughput.
>> > Is it because lower CPU utilization higher packet process rate??
>> 
>> Presumably because the CPU processing required to interact 
>> with the network can becomes a bottleneck; therefore 
>> improving the CPU efficiency should increase the throughput. 
>>  It's been a long time since I read that paper, but when we 
>> did the first driver domains benchmarks in 2004 we were 
>> burning up a significant fraction of the CPU bandwidth of a 
>> 2-way Xeon in order to achieve line rate on gigabit ethernet.
>> 

  Yes, for gigabit NICs both Xen and linux can achieve
  line rate with modern machines
  As we move to 10Gb/s NICs the CPU will become the bottleneck,
  thus reducing the CPU cost should enable Xen to get better
  network throughput.

>> Also, improving the CPU utilisation encountered in the 
>> course of network processing should make more CPU time 
>> available to other work, which would be good.
>> 

  Right! Domains do more than just networking. Freeing cycles
  from the network stack should improve application performance.
  While the experiments are done using a micro network 
  benchamark (netperf), real applications will have to do real
  work in addition to network processing.

>> > Why not show network throught directly??
>> 

  Because it is not interesting. Both Xen and linux can
  saturate a 1 Gb/s NIC and thus achieve the same
  throughput.


>> Presumably in the case of this paper the goal was to 
>> illustrate the kind of measurements that Xenoprof can make 
>> and the improvements in those measurements that can be 
>> achieved with targetted modifications to the codebase.
>> 

  Actually the goal is to improve efficiency of Xen networking,
  to free cycles for the application and to scale to higher 
  network bandwidth (i.e. 10 Gb/s)
 
>> I agree it would have been interesting to see what effects 
>> on the network throughput were but I guess these would vary 
>> between different machines and network loads in any case.
>> 
>> Just my two cents ;-)
>> 
>> Cheers,
>> Mark
>> 
>> --
>> Dave: Just a question. What use is a unicyle with no seat?  
>> And no pedals!
>> Mark: To answer a question with a question: What use is a skateboard?
>> Dave: Skateboards have wheels.
>> Mark: My wheel has a wheel!
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
>> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel