[dpdk-dev] [PATCH v6 07/15] vhost: extract split ring handling from Rx and Tx functions

[Maxime Coquelin]

On 07/04/2018 08:51 AM, Tiwei Bie wrote:
> On Mon, Jul 02, 2018 at 10:16:21AM +0200, Maxime Coquelin wrote:
> [...]
>> +
>> +	if (unlikely(vq->access_ok == 0))
>> +		if (unlikely(vring_translate(dev, vq) < 0))
>> +			goto out;
>> +
>> +
> 
> Please just keep one blank line.
> 
>> +	/*
>> +	 * Construct a RARP broadcast packet, and inject it to the "pkts"
>> +	 * array, to looks like that guest actually send such packet.
>> +	 *
>> +	 * Check user_send_rarp() for more information.
>> +	 *
>> +	 * broadcast_rarp shares a cacheline in the virtio_net structure
>> +	 * with some fields that are accessed during enqueue and
>> +	 * rte_atomic16_cmpset() causes a write if using cmpxchg. This could
>> +	 * result in false sharing between enqueue and dequeue.
>> +	 *
>> +	 * Prevent unnecessary false sharing by reading broadcast_rarp first
>> +	 * and only performing cmpset if the read indicates it is likely to
>> +	 * be set.
>> +	 */
>> +
> 
> Please remove above blank line.
> 
>> +	if (unlikely(rte_atomic16_read(&dev->broadcast_rarp) &&
>> +			rte_atomic16_cmpset((volatile uint16_t *)
>> +				&dev->broadcast_rarp.cnt, 1, 0))) {
>> +
>> +		rarp_mbuf = rte_net_make_rarp_packet(mbuf_pool, &dev->mac);
>> +		if (rarp_mbuf == NULL) {
>> +			RTE_LOG(ERR, VHOST_DATA,
>> +				"Failed to make RARP packet.\n");
>> +			return 0;
>> +		}
>> +		count -= 1;
>> +	}
>> +
>> +	count = virtio_dev_tx_split(dev, vq, mbuf_pool, pkts, count);
>> +
>>   out:
>>   	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
>>   		vhost_user_iotlb_rd_unlock(vq);
>> @@ -1200,10 +1222,10 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
>>   		 * Inject it to the head of "pkts" array, so that switch's mac
>>   		 * learning table will get updated first.
>>   		 */
>> -		memmove(&pkts[1], pkts, i * sizeof(struct rte_mbuf *));
>> +		memmove(&pkts[1], pkts, count * sizeof(struct rte_mbuf *));
>>   		pkts[0] = rarp_mbuf;
>> -		i += 1;
>> +		count += 1;
>>   	}
>>   
>> -	return i;
>> +	return count;
>>   }
>> -- 
>> 2.14.4
>>

Done,

Thanks,
Maxime