netdev - Re: [RFC PATCH v7 01/19] Add a new structure for skb buffer from external.

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Date:	Thu, 24 Jun 2010 20:08:36 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Dong, Eddie" <eddie.dong@...el.com>
Cc:	"Xin, Xiaohui" <xiaohui.xin@...el.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mst@...hat.com" <mst@...hat.com>, "mingo@...e.hu" <mingo@...e.hu>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"jdike@...ux.intel.com" <jdike@...ux.intel.com>
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@...dor.apana.org.au>
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