netdev - Re: [net-next RFC] pktgen: don't wait for the device who doesn't free skb immediately after sent

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Message-ID: <50B46179.4040809@redhat.com>
Date:	Tue, 27 Nov 2012 14:45:13 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	rusty@...tcorp.com.au, mst@...hat.com, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [net-next RFC] pktgen: don't wait for the device who doesn't
 free skb immediately after sent

On 11/27/2012 01:37 AM, Stephen Hemminger wrote:
> On Mon, 26 Nov 2012 15:56:52 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
>> Some deivces do not free the old tx skbs immediately after it has been sent
>> (usually in tx interrupt). One such example is virtio-net which optimizes for
>> virt and only free the possible old tx skbs during the next packet sending. This
>> would lead the pktgen to wait forever in the refcount of the skb if no other
>> pakcet will be sent afterwards.
>>
>> Solving this issue by introducing a new flag IFF_TX_SKB_FREE_DELAY which could
>> notify the pktgen that the device does not free skb immediately after it has
>> been sent and let it not to wait for the refcount to be one.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> Another alternative would be using skb_orphan() and skb->destructor.
> There are other cases where skb's are not freed right away.
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Hi Stephen:

Do you mean registering a skb->destructor for pktgen then set and check 
bits in skb->tx_flag?
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