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Date: Wed, 16 Dec 2009 15:07:53 +1030 From: Rusty Russell <rusty@...tcorp.com.au> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: Herbert Xu <herbert@...dor.apana.org.au>, Sridhar Samudrala <sri@...ibm.com>, netdev@...r.kernel.org Subject: Re: [RFC PATCH] Regression in linux 2.6.32 virtio_net seen with vhost-net On Wed, 16 Dec 2009 10:02:27 am Michael S. Tsirkin wrote: > Right. Hmm. So for this to work we'll need to > 1. Free skb upon interrupt instead of > waiting for the next xmit call > 2. Add API to query free ring capacity > > Rusty, sounds like a good plan? Well, the query stuff is not too bad, but I can't completely convince myself it's race-free. We don't want to do locking. A NAPI-style solution seems cleaner, and I'm testing that now. > We could also extend host to delay interrupt > until there is sufficient TX capacity > but of course we also need to support > old hosts as well. Xen does this, and I rejected it in favor of simple enable/disable flags in the original virtio design. It was probably wrong: while the guest can enable on a "few remaining" heuristic, it's going to have latency. The host can do a more timely decision. There's nothing stopping the Host from doing this heuristic today, of course: the DISABLE flag is advisory only. But let's check the limitations of the guest-enable approach first? Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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