netdev - Re: [PATCH 4/5] virtio_net: add dedicated XDP transmit queues

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Message-ID: <5830C52B.8000108@gmail.com>
Date:   Sat, 19 Nov 2016 13:33:31 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Jakub Kicinski <kubakici@...pl>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     tgraf@...g.ch, shm@...ulusnetworks.com,
        alexei.starovoitov@...il.com, daniel@...earbox.net,
        davem@...emloft.net, john.r.fastabend@...el.com,
        netdev@...r.kernel.org, bblanco@...mgrid.com, brouer@...hat.com
Subject: Re: [PATCH 4/5] virtio_net: add dedicated XDP transmit queues

On 16-11-18 07:23 PM, Jakub Kicinski wrote:
> On Fri, 18 Nov 2016 19:20:58 -0800, Eric Dumazet wrote:
>> On Fri, 2016-11-18 at 18:57 -0800, Jakub Kicinski wrote:
>>> On Fri, 18 Nov 2016 18:43:55 -0800, John Fastabend wrote:  
>>>> On 16-11-18 06:10 PM, Jakub Kicinski wrote:  
>>  [...]  
>>>>
>>>> Seem like a valid concerns to me how about num_possible_cpus() instead.  
>>>
>>> That would solve problem 1, but could cpu_possible_mask still be sparse
>>> on strange setups?  Let me try to dig into this, I recall someone
>>> (Eric?) was fixing similar problems some time ago.  
>>
>> nr_cpu_ids is probably what you want ;)
> 
> Thank you :)
> 

Yep poked around a bit and the common pattern seems to be to use
nr_cpu_ids to build a cpu array and then index it with
smp_processor_id(). So I'll do this as well.

Although I'm not sure I entirely follow on the x86 platforms at
least how/if nr_cpu_ids != num_possible_cpus().

Nice catch Jakub.

Thanks,
John