RE: [RFC PATCH v7 01/19] Add a new structure for skb buffer fromexternal.

[Xin, Xiaohui]

Herbert,
That's why I have sent you the patch for guest virtio-net driver. I reserved 512 bytes in each page, then I can always have the space to copy and avoid the backend memory used up issue.

Thanks
Xiaohui

>-----Original Message-----
>From: Herbert Xu [mailto:herbert@xxxxxxxxxxxxxxxxxxx]
>Sent: Thursday, June 24, 2010 6:09 PM
>To: Dong, Eddie
>Cc: Xin, Xiaohui; Stephen Hemminger; netdev@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
>linux-kernel@xxxxxxxxxxxxxxx; mst@xxxxxxxxxx; mingo@xxxxxxx; davem@xxxxxxxxxxxxx;
>jdike@xxxxxxxxxxxxxxx
>Subject: Re: [RFC PATCH v7 01/19] Add a new structure for skb buffer from external.
>
>On Wed, Jun 23, 2010 at 06:05:41PM +0800, Dong, Eddie wrote:
>>
>> I mean once the frontend side driver post the buffers to the backend driver, the backend
>driver will "immediately" use that buffers to compose skb or gro_frags and post them to the
>assigned host NIC driver as receive buffers. In that case, if the backend driver recieves a
>packet from the NIC that requires to do copy, it may be unable to find additional free guest
>buffer because all of them are already used by the NIC driver. We have to reserve some guest
>buffers for the possible copy even if the buffer address is not identified by original skb :(
>
>OK I see what you mean.  Can you tell me how does Xiaohui's
>previous patch-set deal with this problem?
>
>Thanks,
>--
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>Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
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