From mboxrd@z Thu Jan  1 00:00:00 1970
From: Amos Kong <akong@redhat.com>
Subject: Re: [net-next RFC V5 4/5] virtio_net: multiqueue support
Date: Fri, 06 Jul 2012 04:02:58 +0800
Message-ID: <4FF5F2F2.9050307@redhat.com>
References: <1341484194-8108-1-git-send-email-jasowang@redhat.com>
	<1341484194-8108-5-git-send-email-jasowang@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: krkumar2@in.ibm.com, habanero@linux.vnet.ibm.com, mashirle@us.ibm.com,
	kvm@vger.kernel.org, mst@redhat.com, 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, sri@us.ibm.com
To: Jason Wang <jasowang@redhat.com>
Return-path: <virtualization-bounces@lists.linux-foundation.org>
In-Reply-To: <1341484194-8108-5-git-send-email-jasowang@redhat.com>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/virtualization/>
List-Post: <mailto:virtualization@lists.linux-foundation.org>
List-Help: <mailto:virtualization-request@lists.linux-foundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=subscribe>
Sender: virtualization-bounces@lists.linux-foundation.org
Errors-To: virtualization-bounces@lists.linux-foundation.org
List-Id: netdev.vger.kernel.org

On 07/05/2012 06:29 PM, Jason Wang wrote:
> This patch converts virtio_net to a multi queue device. After negotiated
> VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs,
> and driver could read the number from config space.
> 
> The driver expects the number of rx/tx queue paris is equal to the number of
> vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
> optimization were introduced:
> 
> - Txq selection is based on the processor id in order to avoid contending a lock
>   whose owner may exits to host.
> - Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
>   the queue pairs.
> 
> Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---

...

>  
>  static int virtnet_probe(struct virtio_device *vdev)
>  {
> -	int err;
> +	int i, err;
>  	struct net_device *dev;
>  	struct virtnet_info *vi;
> +	u16 num_queues, num_queue_pairs;
> +
> +	/* Find if host supports multiqueue virtio_net device */
> +	err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
> +				offsetof(struct virtio_net_config,
> +				num_queues), &num_queues);
> +
> +	/* We need atleast 2 queue's */


s/atleast/at least/


> +	if (err || num_queues < 2)
> +		num_queues = 2;
> +	if (num_queues > MAX_QUEUES * 2)
> +		num_queues = MAX_QUEUES;

                num_queues = MAX_QUEUES * 2;

MAX_QUEUES is the limitation of RX or TX.

> +
> +	num_queue_pairs = num_queues / 2;

...

-- 
			Amos.