From: Rusty Russell <rusty@rustcorp•com.au>
To: Tom Herbert <therbert@google•com>
Cc: kvm@vger•kernel.org, "Michael S. Tsirkin" <mst@redhat•com>,
netdev@vger•kernel.org, rick.jones2@hp•com,
virtualization@lists•linux-foundation.org,
levinsasha928@gmail•com, pbonzini@redhat•com
Subject: Re: [PATCHv4] virtio-spec: virtio network device multiqueue support
Date: Wed, 19 Sep 2012 11:10:10 +0930 [thread overview]
Message-ID: <87wqzqpz7p.fsf@rustcorp.com.au> (raw)
In-Reply-To: <CA+mtBx_Kjp62UYJs-7OSFsFKndx6H1oOkuD8U3ooAUuR1PMF=Q@mail.gmail.com>
Tom Herbert <therbert@google•com> writes:
> On Tue, Sep 11, 2012 at 10:49 PM, Rusty Russell <rusty@rustcorp•com.au>wrote:
>> Perhaps Tom can explain how we avoid out-of-order receive for the
>> accelerated RFS case? It's not clear to me, but we need to be able to
>> do that for virtio-net if it implements accelerated RFS.
>
> AFAIK ooo RX is possible with accelerated RFS. We have an algorithm that
> prevents this for RFS case by deferring a migration to a new queue as long
> as it's possible that a flow might have outstanding packets on the old
> queue. I suppose this could be implemented in the device for the HW
> queues, but I don't think it would be easy to cover all cases where packets
> were already in transit to the host or other cases where host and device
> queues are out of sync.
Having gone to such great lengths to avoid ooo for RFS, I don't think
DaveM would be happy if we allow it for virtio_net.
So, how *would* we implement such a thing for a "hardware" device? What
if the device will only change the receive queue if the old receive
queue is empty?
Cheers,
Rusty.
next prev parent reply other threads:[~2012-09-19 1:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-09 13:03 [PATCHv4] virtio-spec: virtio network device multiqueue support Michael S. Tsirkin
2012-09-10 2:12 ` Rusty Russell
2012-09-10 6:16 ` Michael S. Tsirkin
2012-09-10 6:27 ` Michael S. Tsirkin
2012-09-10 6:33 ` Michael S. Tsirkin
2012-09-10 11:00 ` Jason Wang
2012-09-12 5:49 ` Rusty Russell
2012-09-12 7:57 ` Michael S. Tsirkin
2012-09-12 14:40 ` Tom Herbert
2012-09-12 19:11 ` Ben Hutchings
2012-09-12 14:38 ` Tom Herbert
2012-09-19 1:40 ` Rusty Russell [this message]
2012-09-19 6:12 ` Michael S. Tsirkin
2012-09-12 0:29 ` Rusty Russell
2012-09-10 18:39 ` Rick Jones
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