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[Xen-users] Why two netback drivers? (netback/0 and netback/1)

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  • From: "Blazej Adamczyk" <blazej.adamczyk@xxxxxxxxx>
  • Date: Sun, 14 Nov 2010 17:02:26 +0100
  • Delivery-date: Mon, 15 Nov 2010 05:58:48 -0800
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Hello everyone,


I was looking at Xen networking IO architecture and I really don’t understand one thing. On Dom0 right after booting up there are two netback kernel threads (netback/0 and netback/1). As I have noticed, they both share the tasks related with scheduling the traffic for all DomUs. Having two guest domains assigns each netback to a single domain (from my observations). But having more guest domains makes them share these two processes.


Can anyone tell me why there are exactly two netback processes? What part of the Xen code is responsible for creating them and if I can change configuration to have more of them?


There are also loop0, loop1.. processes but they are created for each DomU created and as I can guess they are responsible for connecting eth0 interface with vif interfaces.


The reason I ask this question is that I was wondering if I can set priorities on each DomU network IO operations by changing the scheduling policy on the driver domain.


My configuration is simple:

Domain 0 is also the driver domain. The netback drivers are compiled into the kernel. I use Linux Gentoo and Xen 4.0.


Thanks in advance for any help and comments.


Best regards,


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