Re: [dpdk-dev] [RFC 0/7] PMD driver for AF_XDP

[Jason Wang <jasowang@redhat.com>]

On 2018年03月01日 12:20, Zhang, Qi Z wrote:
> +Magnus, since a typo in my first batch in email address.
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zhang, Qi Z
>> Sent: Thursday, March 1, 2018 12:19 PM
>> To: Jason Wang<jasowang@redhat.com>;dev@dpdk.org
>> Cc:magnus.karlsson@intei.com; Topel, Bjorn<bjorn.topel@intel.com>
>> Subject: Re: [dpdk-dev] [RFC 0/7] PMD driver for AF_XDP
>>
>>
>>
>>> -----Original Message-----
>>> From: Jason Wang [mailto:jasowang@redhat.com]
>>> Sent: Thursday, March 1, 2018 10:52 AM
>>> To: Zhang, Qi Z<qi.z.zhang@intel.com>;dev@dpdk.org
>>> Cc:magnus.karlsson@intei.com; Topel, Bjorn<bjorn.topel@intel.com>
>>> Subject: Re: [dpdk-dev] [RFC 0/7] PMD driver for AF_XDP
>>>
>>>
>>>
>>> On 2018年02月27日 17:32, Qi Zhang wrote:
>>>> The RFC patches add a new PMD driver for AF_XDP which is a proposed
>>>> faster version of AF_PACKET interface in Linux, see below link for
>>>> detail AF_XDP introduction:
>>>> https://fosdem.org/2018/schedule/event/af_xdp/
>>>> https://lwn.net/Articles/745934/
>>>>
>>>> This patchset is base on v18.02.
>>>> It also require a linux kernel that have below AF_XDP RFC patches be
>>>> applied.
>>>> https://patchwork.ozlabs.org/patch/867961/
>>>> https://patchwork.ozlabs.org/patch/867960/
>>>> https://patchwork.ozlabs.org/patch/867938/
>>>> https://patchwork.ozlabs.org/patch/867939/
>>>> https://patchwork.ozlabs.org/patch/867940/
>>>> https://patchwork.ozlabs.org/patch/867941/
>>>> https://patchwork.ozlabs.org/patch/867942/
>>>> https://patchwork.ozlabs.org/patch/867943/
>>>> https://patchwork.ozlabs.org/patch/867944/
>>>> https://patchwork.ozlabs.org/patch/867945/
>>>> https://patchwork.ozlabs.org/patch/867946/
>>>> https://patchwork.ozlabs.org/patch/867947/
>>>> https://patchwork.ozlabs.org/patch/867948/
>>>> https://patchwork.ozlabs.org/patch/867949/
>>>> https://patchwork.ozlabs.org/patch/867950/
>>>> https://patchwork.ozlabs.org/patch/867951/
>>>> https://patchwork.ozlabs.org/patch/867952/
>>>> https://patchwork.ozlabs.org/patch/867953/
>>>> https://patchwork.ozlabs.org/patch/867954/
>>>> https://patchwork.ozlabs.org/patch/867955/
>>>> https://patchwork.ozlabs.org/patch/867956/
>>>> https://patchwork.ozlabs.org/patch/867957/
>>>> https://patchwork.ozlabs.org/patch/867958/
>>>> https://patchwork.ozlabs.org/patch/867959/
>>>>
>>>> There is no clean upstream target yet since kernel patch is still in
>>>> RFC stage, The purpose of the patchset is just for anyone that want
>>>> to eveluate af_xdp with DPDK application and get feedback for
>>>> further improvement.
>>>>
>>>> To try with the new PMD
>>>> 1. compile and install the kernel with above patches applied.
>>>> 2. configure $LINUX_HEADER_DIR (dir of "make headers_install")
>>>>      and $TOOLS_DIR (dir at <kernel_src>/tools) at
>>> driver/net/af_xdp/Makefile
>>>>      before compile DPDK.
>>>> 3. make sure libelf and libbpf is installed.
>>>>
>>>> BTW, performance test shows our PMD can reach 94%~98% of the orignal
>>>> benchmark when share memory is enabled.
>>> Hi:
>>>
>>> Looks like zero copy is not used in this series. Any plan to support that?
>> Zero copy is enabled in patch 5, if a mempool passed check_mempool, it will
>> be registered to af_xdp socket.
>> so there will be no memcpy between mbuf and af_xdp.

Aha, I see. So the zerocopy was limited to some specific use case. And 
if I understand it correctly, zc mode could not be used for VM.

Thanks

>>> If not, what's the advantage compared to vhost-net + tap + XDP_REDIRECT?
>>>
>>> Have you measured l2fwd performance in this case? I believe the number
>>> you refer here is rxdrop (XDP_DRV) which is 11.6Mpps.
>> Actually we measure the performance on rxonly / txonly / l2fwd on i40e with
>> XDP_SKB and XDP_DRV_ZC
>>
>> Regards
>> Qi
>>
>>> Thanks