netdev - Re: [bpf-next V2 PATCH 10/15] xdp: rhashtable with allocator ID to pointer mapping

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Message-ID: <6950eb76-8e3d-60f2-6de1-005a4e4fd3f6@redhat.com>
Date:   Tue, 20 Mar 2018 10:26:50 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     netdev@...r.kernel.org,
        BjörnTöpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, eugenia@...lanox.com,
        John Fastabend <john.fastabend@...il.com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>, galp@...lanox.com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [bpf-next V2 PATCH 10/15] xdp: rhashtable with allocator ID to
 pointer mapping



On 2018年03月19日 17:48, Jesper Dangaard Brouer wrote:
> On Fri, 16 Mar 2018 16:45:30 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
>> On 2018年03月10日 00:07, Jesper Dangaard Brouer wrote:
>>> On Fri, 9 Mar 2018 21:07:36 +0800
>>> Jason Wang <jasowang@...hat.com> wrote:
>>>   
>>>>>>> Use the IDA infrastructure for getting a cyclic increasing ID number,
>>>>>>> that is used for keeping track of each registered allocator per
>>>>>>> RX-queue xdp_rxq_info.
>>>>>>>
>>>>>>> Signed-off-by: Jesper Dangaard Brouer<brouer@...hat.com>
>>>>>> A stupid question is, can we manage to unify this ID with NAPI id?
>>>>> Sorry I don't understand the question?
>>>> I mean can we associate page poll pointer to napi_struct, record NAPI id
>>>> in xdp_mem_info and do lookup through NAPI id?
>>> No. The driver can unreg/reg a new XDP memory model,
>> Is there an actual use case for this?
> I believe this is the common use case.  When attaching an XDP/bpf prog,
> then the driver usually want to change the RX-ring memory model
> (different performance trade off).

Right, but a single driver should only have one XDP memory model. (Or 
you want to all drivers to use this generic allocator?)

> When detaching XDP, then driver
> want to change back to old memory model. During this process, I
> believe, the NAPI-ID remains the same (right?).

Yes, but we can change the allocator pointer in the NAPI struct in this 
case too.

Thanks

>
>>>    without reloading
>>> the NAPI and generate a new NAPI id.
>>>