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

To: Blazej Adamczyk <blazej.adamczyk@xxxxxxxxx>
Subject: Re: [Xen-users] Why two netback drivers? (netback/0 and netback/1)
From: Todd Deshane <deshantm@xxxxxxxxx>
Date: Mon, 15 Nov 2010 10:40:51 -0500
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
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On Sun, Nov 14, 2010 at 11:02 AM, Blazej Adamczyk
<blazej.adamczyk@xxxxxxxxx> wrote:
> 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?

My guess is that for performance reasons, multiple threads are used. I
think that if you are really trying to get a better sense of how it is
working internally and how it can be tweaked, then the xen-devel list
would be a better place to discuss such issues.

Hope that helps.


> 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,
> Blazej
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users

Todd Deshane

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