On Mon, 03 Dec 2012 14:45:46 +0800 Jason Wang <jasowang@xxxxxxxxxx> wrote: > On Tuesday, November 27, 2012 08:49:19 AM Stephen Hemminger wrote: > > On Tue, 27 Nov 2012 14:45:13 +0800 > > > > Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > On 11/27/2012 01:37 AM, Stephen Hemminger wrote: > > > > On Mon, 26 Nov 2012 15:56:52 +0800 > > > > > > > > Jason Wang <jasowang@xxxxxxxxxx> 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@xxxxxxxxxx> > > > > > > > > Another alternative would be using skb_orphan() and skb->destructor. > > > > There are other cases where skb's are not freed right away. > > > > -- > > > > To unsubscribe from this list: send the line "unsubscribe netdev" in > > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > Hi Stephen: > > > > > > Do you mean registering a skb->destructor for pktgen then set and check > > > bits in skb->tx_flag? > > > > Yes. Register a destructor that does something like update a counter (number > > of packets pending), then just spin while number of packets pending is over > > threshold. > > Have some experiments on this, looks like it does not work weel when clone_skb > is used. For driver that call skb_orphan() in ndo_start_xmit, the destructor > is only called when the first packet were sent, but what we need to know is > when the last were sent. Any thoughts on this or we can just introduce another > flag (anyway we have something like IFF_TX_SKB_SHARING) ? > The SKB_SHARING flag looks like the best solution then. Surprisingly, transmit buffer completion is a major bottleneck for 10G devices, and I suspect more changes will come. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
