netdev - Re: [RFC PATCH net-next 3/3] virtio-net: Add accelerated RFS support

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Date:	Fri, 17 Jan 2014 06:00:33 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	Tom Herbert <therbert@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH net-next 3/3] virtio-net: Add accelerated RFS support

On Fri, Jan 17, 2014 at 5:31 AM, Ben Hutchings
<bhutchings@...arflare.com> wrote:
> On Wed, 2014-01-15 at 22:20 +0800, Zhi Yong Wu wrote:
> [...]
>> +static int virtnet_init_rx_cpu_rmap(struct virtnet_info *vi)
>> +{
>> +     int rc = 0;
>> +
>> +#ifdef CONFIG_RFS_ACCEL
>> +     struct virtio_device *vdev = vi->vdev;
>> +     unsigned int irq;
>> +     int i;
>> +
>> +     if (!vi->affinity_hint_set)
>> +             goto out;
>> +
>> +     vi->dev->rx_cpu_rmap = alloc_irq_cpu_rmap(vi->max_queue_pairs);
>> +     if (!vi->dev->rx_cpu_rmap) {
>> +             rc = -ENOMEM;
>> +             goto out;
>> +     }
>> +
>> +     for (i = 0; i < vi->max_queue_pairs; i++) {
>> +             irq = virtqueue_get_vq_irq(vdev, vi->rq[i].vq);
>> +             if (irq == -1)
>> +                     goto failed;
>
> Jumping into an if-statement is confusing.  Also do you really want to
> return 0 in this case?
No, If it fail to get irq, i want it to exit as soon as possible,
otherwise it will cause irq_cpu_rmap_add() to be invoked with one
incorrect argument irq.

By the way, do you have thought about if it makes sense to add aRFS
support to virtio_net? For [patch 2/3], what do you think of those
missing stuff listed by me?
For how indirect table is implemented in sfc NIC, do you have any doc
to share with  me? thanks.

>
> Otherwise this looks fine.
>
> Ben.
>
>> +             rc = irq_cpu_rmap_add(vi->dev->rx_cpu_rmap, irq);
>> +             if (rc) {
>> +failed:
>> +                     virtnet_free_irq_cpu_rmap(vi);
>> +                     goto out;
>> +             }
>> +     }
>> +out:
>> +#endif
>> +     return rc;
>> +}
> [...]
>
> --
> Ben Hutchings, Staff Engineer, Solarflare
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.
>



-- 
Regards,

Zhi Yong Wu
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