Re: Re: Re: Re: [Xen-devel] SetPageForeign in netback

["Grzegorz Miłoś" <gm281@xxxxxxxxx>]

>>The reason why you have to copy is to make sure that you pull the skb
>>into a fresh page (which doesn't have any other pieces of data in it).
>>It's only then that you can flip it to DomU.
>>It used to be the case that the backend was more efficient in the
>>rx-flip mode. Some/most skbs copies were avoided by keeping a close
>>eye on the skb allocation. Since rx-flip is now only/mostly kept for
>>backward compatibility (rx-copy is the default) the code was
>>simplified.
>
> You mean in previous Xen release, rx-flip is more efficient than today's 
> release. And keeping rx-flip in Xen Source Code tree today is only for 
> compatibility. So no need to do more optimizing for it.
> Is my understanding right?
>

I don't know if much performance was lost (the code got simplified, at
the expense of potentially more skb copies, but I don't know of any
experimental tests to benchmark what the effect was exactly), but
aside from that, your understanding is correct.

Cheers
Gr(z)egor(z)

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