Re: [Xen-devel] The data transfer speed between two VMs -- a comparison between Xen libvchan and SCP?

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Sat, Mar 22, 2014 at 4:28 PM, Bei Guan <gbtju85@xxxxxxxxx> wrote:
> Hi All,
>
> I try to make a comparison between the Xen libvchan and SCP with respect to
> the data transfer speed between two co-located VMs. The following is what I
> have done.
> 1. I modify the code tools/libvchan/node.c to transfer a file between two PV
> DomUs. I set the buffer size to 2048, which is the data size writing into
> the shared ring every time. (Please refer to the line 78 in node.cï
> 2. I use the command "time" to get the rough time of transferring a file
> between two PV DomUs under the SCP and Xen libvchan. The size of the file to
> transfer is 50M, 100M, 500M. The test result is posted behind.
>
> However, I find that the data transferred time does decrease much under the
> Xen libvchan when compared to the SCP. I also set the buffer size to 4096,
> 5000, 10000, and so on. The Xen libvchan doesn't show a better performance.
> It doesn't perform "around 30-40% faster than TCP for 4KB request sizes".
> (Like the paper[1] said.)
>
> Is there any wrong with my test? How to show the advantage of the Xen
> libvchan? Or  say the advantage of the shared memory mechanism between Xen
> PV DomUs?
>
> [1] "The case for reconfigurable I/O channels"
> http://www.freebsdlabs.com/~robert/papers/201203-resolve-reconfigurable-io.pdf

I think your best bet is to cc the authors of the paper with that
question, and see if they can give you any insight.

 -George

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