From: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Date: Mon, 18 May 2009 22:18:47 +0930 > We check for finished xmit skbs on every xmit, or on a timer (unless > the host promises to force an interrupt when the xmit ring is empty). > This can penalize userspace tasks which fill their sockbuf. Not much > difference with TSO, but measurable with large numbers of packets. > > There are a finite number of packets which can be in the transmission > queue. We could fire the timer more than every 100ms, but that would > just hurt performance for a corner case. This seems neatest. ... > Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> If this is so great for virtio it would also be a great idea universally, but we don't do it. What you're doing by orphan'ing is creating a situation where a single UDP socket can loop doing sends and monopolize the TX queue of a device. The only control we have over a sender for fairness in datagram protocols is that send buffer allocation. I'm guilty of doing this too in the NIU driver, also because there I lack a "TX queue empty" interrupt and this can keep TCP sockets from getting stuck. I think we need a generic solution to this issue because it is getting quite common to see cases where the packets in the TX queue of a device can sit there indefinitely. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
