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

From: Xin, Xiaohui
Date: Thu Jun 24 2010 - 22:08:47 EST

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.


>-----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;
>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?
>Visit Openswan at
>Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
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