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From: Jason Wang <jasowang@redhat.com>
To: David Ahern <dsahern@gmail.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>
Cc: "xdp-newbies@vger.kernel.org" <xdp-newbies@vger.kernel.org>
Subject: Re: error loading xdp program on virtio nic
Date: Mon, 25 Nov 2019 10:48:19 +0800	[thread overview]
Message-ID: <8041b387-5cfb-7a57-fc01-9be6967d8658@redhat.com> (raw)
In-Reply-To: <8324a37e-5507-2ae6-53f6-949c842537e0@gmail.com>


On 2019/11/22 下午11:43, David Ahern wrote:
> On 11/21/19 11:09 PM, Jason Wang wrote:
>>> Doubling the number of queues for each tap device adds overhead to the
>>> hypervisor if you only want to allow XDP_DROP or XDP_DIRECT. Am I
>>> understanding that correctly?
>>
>> Yes, but there's almost impossible to know whether or not XDP_TX will be
>> used by the program. If we don't use per CPU TX queue, it must be
>> serialized through locks, not sure it's worth try that (not by default,
>> of course).
>>
> This restriction is going to prevent use of XDP in VMs in general cloud
> hosting environments. 2x vhost threads for vcpus is a non-starter.
>
> If one XDP feature has high resource needs, then we need to subdivide
> the capabilities to let some work and others fail. For example, a flag
> can be added to xdp_buff / xdp_md that indicates supported XDP features.
> If there are insufficient resources for XDP_TX, do not show support for
> it. If a program returns XDP_TX anyways, packets will be dropped.
>

Or we can just:
- If queues is sufficient, using per-cpu TX queue
- If not, synchronize through spinlocks (like what TAP did right now, 
since there's no easy way to have more queues on the fly)

Thanks

      parent reply	other threads:[~2019-11-25  2:48 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-20 17:52 error loading xdp program on virtio nic David Ahern
2019-11-21  3:26 ` Jason Wang
2019-11-21  3:35   ` David Ahern
2019-11-21  3:54     ` Jason Wang
2019-11-21  4:05       ` David Ahern
2019-11-21  6:26         ` Jesper Dangaard Brouer
2019-11-21  7:02           ` Jason Wang
2019-11-21 15:49             ` David Ahern
2019-11-22  6:09               ` Jason Wang
2019-11-22 15:43                 ` David Ahern
2019-11-22 16:50                   ` Jakub Kicinski
2019-11-22 16:57                   ` Jesper Dangaard Brouer
2019-11-22 17:42                     ` David Ahern
2019-11-23 13:27                       ` Toke Høiland-Jørgensen
2019-11-23 13:27                         ` Toke Høiland-Jørgensen
2019-11-25  2:42                     ` Jason Wang
2019-11-25  2:48                   ` Jason Wang [this message]

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