Re: [PATCHv3 0/6] tun zerocopy support
From: David Miller
Date: Sun Jul 22 2012 - 15:40:15 EST
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Date: Sun, 22 Jul 2012 01:05:34 +0300
> I agree a small win in CPU use is nothing to write home about,
> I don't yet understand why the win is so small - macvtap has zero copy
> supported for a while and it has exactly same issues.
> I hope adding tun zerocopy support upstream will help us
> make progress faster and find the bottleneck, so far not many people use
> macvtap so zero copy mode there didn't make progress.
> I do know why local performance regresses with zero copy enabled:
> instead of plain copy to user we got get user pages and then memcpy.
> We'll need some logic here to detect this and turn off zero copy.
> The core patches will also be helpful for Ian's more ambitious work.
> Overall I think it's a step in the right direction and it's easier to
> work if core parts are upstream, but if you think we need to wait
> until the gains are more significant, I understand that too.
Ok, I've applied this series, let's see what happens.
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