From: Sasha Levin <levinsasha928@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
mashirle@us.ibm.com, krkumar2@in.ibm.com,
habanero@linux.vnet.ibm.com, rusty@rustcorp.com.au,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, edumazet@google.com,
tahm@linux.vnet.ibm.com, jwhan@filewood.snu.ac.kr,
davem@davemloft.net, akong@redhat.com, kvm@vger.kernel.org,
sri@us.ibm.com
Subject: Re: [net-next RFC V5 4/5] virtio_net: multiqueue support
Date: Mon, 30 Jul 2012 15:00:29 +0200 [thread overview]
Message-ID: <5016856D.8060009@gmail.com> (raw)
In-Reply-To: <20120729094451.GB8977@redhat.com>
On 07/29/2012 11:44 AM, Michael S. Tsirkin wrote:
> On Sat, Jul 21, 2012 at 02:02:58PM +0200, Sasha Levin wrote:
>> On 07/20/2012 03:40 PM, Michael S. Tsirkin wrote:
>>>> - err = init_vqs(vi);
>>>>> + if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
>>>>> + vi->has_cvq = true;
>>>>> +
>>> How about we disable multiqueue if there's no cvq?
>>> Will make logic a bit simpler, won't it?
>>
>> multiqueues don't really depend on cvq. Does this added complexity really justifies adding an artificial limit?
>
> Well !cvq support is a legacy feature: the reason we support it
> in driver is to avoid breaking on old hosts. Adding more code to that
> path just doesn't make much sense since old hosts won't have mq.
Is it really a legacy feature? The spec suggests that its an optional queue which is not necessary for the operation of the device.
Which is why we never implemented it in lkvm - we weren't interested in any of the features it provided at that time and we could provide high performance with vhost support even without it.
WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <levinsasha928@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: krkumar2@in.ibm.com, habanero@linux.vnet.ibm.com,
kvm@vger.kernel.org, netdev@vger.kernel.org, mashirle@us.ibm.com,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, edumazet@google.com,
tahm@linux.vnet.ibm.com, jwhan@filewood.snu.ac.kr,
davem@davemloft.net, sri@us.ibm.com
Subject: Re: [net-next RFC V5 4/5] virtio_net: multiqueue support
Date: Mon, 30 Jul 2012 15:00:29 +0200 [thread overview]
Message-ID: <5016856D.8060009@gmail.com> (raw)
In-Reply-To: <20120729094451.GB8977@redhat.com>
On 07/29/2012 11:44 AM, Michael S. Tsirkin wrote:
> On Sat, Jul 21, 2012 at 02:02:58PM +0200, Sasha Levin wrote:
>> On 07/20/2012 03:40 PM, Michael S. Tsirkin wrote:
>>>> - err = init_vqs(vi);
>>>>> + if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
>>>>> + vi->has_cvq = true;
>>>>> +
>>> How about we disable multiqueue if there's no cvq?
>>> Will make logic a bit simpler, won't it?
>>
>> multiqueues don't really depend on cvq. Does this added complexity really justifies adding an artificial limit?
>
> Well !cvq support is a legacy feature: the reason we support it
> in driver is to avoid breaking on old hosts. Adding more code to that
> path just doesn't make much sense since old hosts won't have mq.
Is it really a legacy feature? The spec suggests that its an optional queue which is not necessary for the operation of the device.
Which is why we never implemented it in lkvm - we weren't interested in any of the features it provided at that time and we could provide high performance with vhost support even without it.
next prev parent reply other threads:[~2012-07-30 13:00 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-05 10:29 [net-next RFC V5 0/5] Multiqueue virtio-net Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-05 10:29 ` [net-next RFC V5 1/5] virtio_net: Introduce VIRTIO_NET_F_MULTIQUEUE Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-05 10:29 ` [net-next RFC V5 2/5] virtio_ring: move queue_index to vring_virtqueue Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-05 11:40 ` Sasha Levin
2012-07-05 11:40 ` Sasha Levin
2012-07-06 3:17 ` Jason Wang
2012-07-06 3:17 ` Jason Wang
2012-07-26 8:20 ` Paolo Bonzini
2012-07-26 8:20 ` Paolo Bonzini
2012-07-30 3:30 ` Jason Wang
2012-07-30 3:30 ` Jason Wang
2012-07-05 10:29 ` [net-next RFC V5 3/5] virtio: intorduce an API to set affinity for a virtqueue Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-27 14:38 ` Paolo Bonzini
2012-07-27 14:38 ` Paolo Bonzini
2012-07-29 20:40 ` Michael S. Tsirkin
2012-07-29 20:40 ` Michael S. Tsirkin
2012-07-30 6:27 ` Paolo Bonzini
2012-08-09 15:14 ` Paolo Bonzini
2012-08-09 15:14 ` Paolo Bonzini
2012-08-09 15:13 ` Paolo Bonzini
2012-08-09 15:13 ` Paolo Bonzini
2012-08-09 15:35 ` Avi Kivity
2012-08-09 15:35 ` Avi Kivity
2012-07-05 10:29 ` [net-next RFC V5 4/5] virtio_net: multiqueue support Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-05 20:02 ` Amos Kong
2012-07-05 20:02 ` Amos Kong
2012-07-06 7:45 ` Jason Wang
2012-07-06 7:45 ` Jason Wang
2012-07-20 13:40 ` Michael S. Tsirkin
2012-07-20 13:40 ` Michael S. Tsirkin
2012-07-21 12:02 ` Sasha Levin
2012-07-21 12:02 ` Sasha Levin
2012-07-23 5:54 ` Jason Wang
2012-07-23 5:54 ` Jason Wang
2012-07-23 9:28 ` Sasha Levin
2012-07-23 9:28 ` Sasha Levin
2012-07-30 3:29 ` Jason Wang
2012-07-30 3:29 ` Jason Wang
2012-07-29 9:44 ` Michael S. Tsirkin
2012-07-29 9:44 ` Michael S. Tsirkin
2012-07-30 3:26 ` Jason Wang
2012-07-30 3:26 ` Jason Wang
2012-07-30 13:00 ` Sasha Levin [this message]
2012-07-30 13:00 ` Sasha Levin
2012-07-23 5:48 ` Jason Wang
2012-07-23 5:48 ` Jason Wang
2012-07-29 9:50 ` Michael S. Tsirkin
2012-07-29 9:50 ` Michael S. Tsirkin
2012-07-30 5:15 ` Jason Wang
2012-07-30 5:15 ` Jason Wang
2012-07-05 10:29 ` [net-next RFC V5 5/5] virtio_net: support negotiating the number of queues through ctrl vq Jason Wang
2012-07-05 10:29 ` Jason Wang
2012-07-05 12:51 ` Sasha Levin
2012-07-05 12:51 ` Sasha Levin
2012-07-05 20:07 ` Amos Kong
2012-07-05 20:07 ` Amos Kong
2012-07-06 7:46 ` Jason Wang
2012-07-06 7:46 ` Jason Wang
2012-07-06 3:20 ` Jason Wang
2012-07-06 3:20 ` Jason Wang
2012-07-06 6:38 ` Stephen Hemminger
2012-07-06 6:38 ` Stephen Hemminger
2012-07-06 9:26 ` Jason Wang
2012-07-06 9:26 ` Jason Wang
2012-07-06 8:10 ` Sasha Levin
2012-07-06 8:10 ` Sasha Levin
2012-07-09 20:13 ` Ben Hutchings
2012-07-09 20:13 ` Ben Hutchings
2012-07-20 12:33 ` Michael S. Tsirkin
2012-07-20 12:33 ` Michael S. Tsirkin
2012-07-23 5:32 ` Jason Wang
2012-07-23 5:32 ` Jason Wang
2012-07-05 17:45 ` [net-next RFC V5 0/5] Multiqueue virtio-net Rick Jones
2012-07-05 17:45 ` Rick Jones
2012-07-06 7:42 ` Jason Wang
2012-07-06 7:42 ` Jason Wang
2012-07-06 16:23 ` Rick Jones
2012-07-06 16:23 ` Rick Jones
2012-07-09 3:23 ` Jason Wang
2012-07-09 3:23 ` Jason Wang
2012-07-09 16:46 ` Rick Jones
2012-07-09 16:46 ` Rick Jones
2012-07-08 8:19 ` Ronen Hod
2012-07-08 8:19 ` Ronen Hod
2012-07-09 5:35 ` Jason Wang
2012-07-09 5:35 ` Jason Wang
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