Re: [dpdk-dev] [PATCH v3] examples/vhost: remove async inflight packet counter

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 2/3/21 1:11 PM, Jiang, Cheng1 wrote:
> Hi,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Wednesday, February 3, 2021 5:52 PM
>> To: Jiang, Cheng1 <cheng1.jiang@intel.com>; Xia, Chenbo
>> <chenbo.xia@intel.com>
>> Cc: dev@dpdk.org; Hu, Jiayu <jiayu.hu@intel.com>; Yang, YvonneX
>> <yvonnex.yang@intel.com>; Wang, Yinan <yinan.wang@intel.com>
>> Subject: Re: [PATCH v3] examples/vhost: remove async inflight packet
>> counter
>>
>>
>>
>> On 2/2/21 7:17 AM, Cheng Jiang wrote:
>>> Remove async inflight packet counter since there is no need to keep
>>> tracking it. Increase MAX_ENQUEUED_SIZE to prevent packet segment
>>> number tracking ring from being exhausted.
>>
>> Is that an optimization or a fix?
>>
>> If the former, let's move it to v21.05.
>>
> 
> I think it's a fix since there is no need to keep the inflight packet counter, sorry I forget adding the fixes, I can submit a v4 to fix it.
OK
>>>
>>> Fixes: a68ba8e0a6b6 ("examples/vhost: refactor vhost data path")
>>>
>>> Signed-off-by: Cheng Jiang <Cheng1.jiang@intel.com>
>>> ---
>>> v3: fixed fixes commit id in git log
>>>
>>> v2: fixed a typo
>>>
>>>  examples/vhost/ioat.h |  2 +-
>>>  examples/vhost/main.c | 10 +---------  examples/vhost/main.h |  1 -
>>>  3 files changed, 2 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/examples/vhost/ioat.h b/examples/vhost/ioat.h index
>>> 0a1dbb811..1aa28ed6a 100644
>>> --- a/examples/vhost/ioat.h
>>> +++ b/examples/vhost/ioat.h
>>> @@ -11,7 +11,7 @@
>>>
>>>  #define MAX_VHOST_DEVICE 1024
>>>  #define IOAT_RING_SIZE 4096
>>> -#define MAX_ENQUEUED_SIZE 512
>>> +#define MAX_ENQUEUED_SIZE 4096
>>
>> Basically, this the size of the ring size, correct?
>> It might be further simplified then.
>>
> 
> Yes, it's a the size of packet tracking ring, and it should be no less then IOAT_RING_SIZE for some corner cases.
> I'm not sure I understand what you mean by saying It might be further simplified then.

I meant maybe in this case just use IOAT_RING_SIZE?

> Thanks,
> Cheng
> 
>>>
>>>  struct dma_info {
>>>  	struct rte_pci_addr addr;
>>> diff --git a/examples/vhost/main.c b/examples/vhost/main.c index
>>> e74fc8750..ca73e7086 100644
>>> --- a/examples/vhost/main.c
>>> +++ b/examples/vhost/main.c
>>> @@ -831,11 +831,8 @@ complete_async_pkts(struct vhost_dev *vdev)
>>>
>>>  	complete_count = rte_vhost_poll_enqueue_completed(vdev->vid,
>>>  					VIRTIO_RXQ, p_cpl,
>> MAX_PKT_BURST);
>>> -	if (complete_count) {
>>> -		__atomic_sub_fetch(&vdev->nr_async_pkts,
>> complete_count,
>>> -			__ATOMIC_SEQ_CST);
>>> +	if (complete_count)
>>>  		free_pkts(p_cpl, complete_count);
>>> -	}
>>>  }
>>>
>>>  static __rte_always_inline void
>>> @@ -878,8 +875,6 @@ drain_vhost(struct vhost_dev *vdev)
>>>  		complete_async_pkts(vdev);
>>>  		ret = rte_vhost_submit_enqueue_burst(vdev->vid,
>> VIRTIO_RXQ,
>>>  					m, nr_xmit, m_cpu_cpl,
>> &cpu_cpl_nr);
>>> -		__atomic_add_fetch(&vdev->nr_async_pkts, ret -
>> cpu_cpl_nr,
>>> -				__ATOMIC_SEQ_CST);
>>>
>>>  		if (cpu_cpl_nr)
>>>  			free_pkts(m_cpu_cpl, cpu_cpl_nr);
>>> @@ -1210,9 +1205,6 @@ drain_eth_rx(struct vhost_dev *vdev)
>>>  		enqueue_count = rte_vhost_submit_enqueue_burst(vdev-
>>> vid,
>>>  					VIRTIO_RXQ, pkts, rx_count,
>>>  					m_cpu_cpl, &cpu_cpl_nr);
>>> -		__atomic_add_fetch(&vdev->nr_async_pkts,
>>> -					enqueue_count - cpu_cpl_nr,
>>> -					__ATOMIC_SEQ_CST);
>>>  		if (cpu_cpl_nr)
>>>  			free_pkts(m_cpu_cpl, cpu_cpl_nr);
>>>
>>> diff --git a/examples/vhost/main.h b/examples/vhost/main.h index
>>> 2d6c05fd7..0ccdce4b4 100644
>>> --- a/examples/vhost/main.h
>>> +++ b/examples/vhost/main.h
>>> @@ -51,7 +51,6 @@ struct vhost_dev {
>>>  	uint64_t features;
>>>  	size_t hdr_len;
>>>  	uint16_t nr_vrings;
>>> -	uint64_t nr_async_pkts;
>>>  	struct rte_vhost_memory *mem;
>>>  	struct device_statistics stats;
>>>  	TAILQ_ENTRY(vhost_dev) global_vdev_entry;
>>> --
>>> 2.29.2
>>>
>