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From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: "Xia, Chenbo" <chenbo.xia@intel.com>,
	"Eugenio Pérez" <eperezma@redhat.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Pei Zhang <pezhang@redhat.com>,
	Jason Wang <jasowang@redhat.com>
Subject: Re: [dpdk-dev] [PATCH] vhost: Clean iotlb cache on vring stop
Date: Thu, 23 Sep 2021 10:50:02 +0200	[thread overview]
Message-ID: <f1b95093-0144-a95b-da46-9f118506a6b5@redhat.com> (raw)
In-Reply-To: <MN2PR11MB4063CA19BF7C6C8B57814A0E9CA39@MN2PR11MB4063.namprd11.prod.outlook.com>



On 9/23/21 10:48, Xia, Chenbo wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Thursday, September 23, 2021 4:34 PM
>> To: Eugenio Pérez <eperezma@redhat.com>; Xia, Chenbo <chenbo.xia@intel.com>
>> Cc: dev@dpdk.org; Pei Zhang <pezhang@redhat.com>; Jason Wang
>> <jasowang@redhat.com>
>> Subject: Re: [PATCH] vhost: Clean iotlb cache on vring stop
>>
>>
>>
>> On 8/27/21 18:12, Eugenio Pérez wrote:
>>> Old IOVA cache entries are left when there is a change on virtio driver
>>> in VM. In case that all these old entries have iova addresses lesser
>>> than new iova entries, vhost code will need to iterate all the cache to
>>> find the new ones. In case of just a new iova entry needed for the new
>>> translations, this condition will last forever.
>>>
>>> This has been observed in virtio-net to testpmd's vfio-pci driver
>>> transition, reducing the performance from more than 10Mpps to less than
>>> 0.07Mpps if the hugepage address was higher than the networking
>>> buffers. Since all new buffers are contained in this new gigantic page,
>>> vhost needs to scan IOTLB_CACHE_SIZE - 1 for each translation at worst.
>>>
>>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
>>> Reported-by: Pei Zhang <pezhang@redhat.com>
>>> ---
>>>    lib/vhost/vhost_user.c | 2 ++
>>>    1 file changed, 2 insertions(+)
>>>
>>> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
>>> index 29a4c9af60..7de48f5333 100644
>>> --- a/lib/vhost/vhost_user.c
>>> +++ b/lib/vhost/vhost_user.c
>>> @@ -2113,6 +2113,8 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
>>>    	msg->size = sizeof(msg->payload.state);
>>>    	msg->fd_num = 0;
>>>
>>> +	vhost_user_iotlb_flush_all(vq);
>>> +
>>>    	vring_invalidate(dev, vq);
>>>
>>>    	return RTE_VHOST_MSG_RESULT_REPLY;
>>>
>>
>> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> 
> So you will fix title and add fix tag when applying, right?

Yes, I will. Thanks for the heads-up!

Maxime

> /Chenbo
> 
>>
>> Thanks,
>> Maxime
> 


  reply	other threads:[~2021-09-23  8:50 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 16:12 Eugenio Pérez
2021-08-30 11:57 ` Xia, Chenbo
2021-08-30 18:10   ` Eugenio Perez Martin
2021-08-31  2:02     ` Xia, Chenbo
2021-08-31  7:10       ` Eugenio Perez Martin
2021-09-23  8:34 ` Maxime Coquelin
2021-09-23  8:48   ` Xia, Chenbo
2021-09-23  8:50     ` Maxime Coquelin [this message]
2021-09-23  8:54       ` Xia, Chenbo
2021-09-28 15:29 ` Maxime Coquelin

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