Re: [dpdk-dev] [PATCH] vhost: notify guest to fill buffer when there is no buffer

[Linhaifeng <haifeng.lin@huawei.com>]

Hi,xie & xu

I found that the new code had try to notify guest after send each packet after 2bbb811.
So this bug not exist now.

static inline uint32_t __attribute__((always_inline))
virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
	struct rte_mbuf **pkts, uint32_t count)
{
	... ...

	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {

		... ...

		/* Kick the guest if necessary. */
		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
			eventfd_write((int)vq->kickfd, 1);
	}

	return count;
}

thank you very much!

On 2015/1/30 16:20, Xu, Qian Q wrote:
> Haifeng
> Could you give more information so that we can reproduce your issue? Thanks. 
> 1. What's your dpdk package, based on which branch, with Huawei's vhost-user's patches? 
> 2. What's your step and command to launch vhost sample? 
> 3. What is mz? Your internal tool? I can't yum install mz or download mz tool. 
> 4. As to your test scenario, I understand it in this way: virtio1 in VM1, virtio2 in VM2, then let virtio1 send packages to virtio2, the problem is that after 3 hours, virtio2 can't receive packets, but virtio1 is still sending packets, am I right? So mz is like a packet generator to send packets, right? 
> 
> 
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Linhaifeng
> Sent: Thursday, January 29, 2015 9:51 PM
> To: Xie, Huawei; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] vhost: notify guest to fill buffer when there is no buffer
> 
> 
> 
> On 2015/1/29 21:00, Xie, Huawei wrote:
>>
>>
>>> -----Original Message-----
>>> From: Linhaifeng [mailto:haifeng.lin@huawei.com]
>>> Sent: Thursday, January 29, 2015 8:39 PM
>>> To: Xie, Huawei; dev@dpdk.org
>>> Subject: Re: [dpdk-dev] [PATCH] vhost: notify guest to fill buffer 
>>> when there is no buffer
>>>
>>>
>>>
>>> On 2015/1/29 18:39, Xie, Huawei wrote:
>>>
>>>>> -		if (count == 0)
>>>>> +		/* If there is no buffers we should notify guest to fill.
>>>>> +		* This is need when guest use virtio_net driver(not pmd).
>>>>> +		*/
>>>>> +		if (count == 0) {
>>>>> +			if (!(vq->avail->flags &
>>>>> VRING_AVAIL_F_NO_INTERRUPT))
>>>>> +				eventfd_write((int)vq->kickfd, 1);
>>>>>  			return 0;
>>>>> +		}
>>>>
>>>> Haifeng:
>>>> Is it the root cause and is it protocol required?
>>>> Could you give a detailed description for that scenario?
>>>>
>>>
>>> I use mz to send data from one VM1 to VM2.The two VM use virtio-net driver.
>>> VM1 execute follow script:
>>> for((i=0;i<999999999;i++));
>>> do
>>> mz eth0 -t udp -A 1.1.1.1 -B 1.1.1.2 -a 00:00:00:00:00:01 -b 
>>> 00:00:00:00:00:02 -c
>>> 10000000 -p 512
>>> sleep 4
>>> done
>>>
>>> VM2 execute follow command to watch:
>>> watch -d ifconfig
>>>
>>> After many hours VM2 stop to receive data.
>>>
>>> Could you test it ?
>>
>>
>> We could try next week after I send the whole patch. 
>> How many hours? Is it reproducible at your side? I inject packets through packet generator to guest for more than ten hours, haven't met issues. 
> 
> About three hours.
> What kind of driver you used in guest?virtio-net-pmd or virtio-net?
> 
> 
>> As I said in another mail sent  to you, could you dump the status of vring if you still have the spot?
> 
> How to dump the status of vring in guest?
> 
>> Could you please also reply to that mail?
>>
> 
> Which mail?
> 
> 
>> For the patch, if we have no root cause, I prefer not to apply it, so that we don't send more interrupts than needed to guest to affect performance.
> 
> I found that if we add this notify the performance is better(growth of 100kpps when use 64byte UDP packets)
> 
>> People could temporarily apply this patch as a work around.
>>
>> Or anyone
>>
> 
> OK.I'm also not sure about this bug.I think i should do something to found the real reason.
> 
>>
>>> --
>>> Regards,
>>> Haifeng
>>
>>
>>
> 

-- 
Regards,
Haifeng