From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Eelco Chaudron <echaudro@redhat.com>,
Jesper Dangaard Brouer <brouer@redhat.com>
Cc: "Machulsky\, Zorik" <zorik@amazon.com>, "Jubran\,
Samih" <sameehj@amazon.com>,
davem@davemloft.net, netdev@vger.kernel.org, "Woodhouse\,
David" <dwmw@amazon.co.uk>, "Matushevsky\,
Alexander" <matua@amazon.com>, "Bshara\,
Saeed" <saeedb@amazon.com>, "Wilson\, Matt" <msw@amazon.com>,
"Liguori\, Anthony" <aliguori@amazon.com>, "Bshara\,
Nafea" <nafea@amazon.com>, "Tzalik\, Guy" <gtzalik@amazon.com>,
"Belgazal\, Netanel" <netanel@amazon.com>, "Saidi\,
Ali" <alisaidi@amazon.com>, "Herrenschmidt\,
Benjamin" <benh@amazon.com>, "Kiyanovski\,
Arthur" <akiyano@amazon.com>,
Daniel Borkmann <borkmann@iogearbox.net>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Jakub Kicinski <jakub.kicinski@netronome.com>,
xdp-newbies@vger.kernel.org
Subject: Re: XDP multi-buffer incl. jumbo-frames (Was: [RFC V1 net-next 1/1] net: ena: implement XDP drop support)
Date: Fri, 28 Jun 2019 09:46:45 +0200 [thread overview]
Message-ID: <87y31m884a.fsf@toke.dk> (raw)
In-Reply-To: <CC99D6DE-5B6B-42F3-8D68-7F9AFF1712FF@redhat.com>
"Eelco Chaudron" <echaudro@redhat.com> writes:
> On 26 Jun 2019, at 10:38, Jesper Dangaard Brouer wrote:
>
>> On Tue, 25 Jun 2019 03:19:22 +0000
>> "Machulsky, Zorik" <zorik@amazon.com> wrote:
>>
>>> On 6/23/19, 7:21 AM, "Jesper Dangaard Brouer" <brouer@redhat.com>
>>> wrote:
>>>
>>> On Sun, 23 Jun 2019 10:06:49 +0300 <sameehj@amazon.com> wrote:
>>>
>>> > This commit implements the basic functionality of drop/pass
>>> logic in the
>>> > ena driver.
>>>
>>> Usually we require a driver to implement all the XDP return
>>> codes,
>>> before we accept it. But as Daniel and I discussed with Zorik
>>> during
>>> NetConf[1], we are going to make an exception and accept the
>>> driver
>>> if you also implement XDP_TX.
>>>
>>> As we trust that Zorik/Amazon will follow and implement
>>> XDP_REDIRECT
>>> later, given he/you wants AF_XDP support which requires
>>> XDP_REDIRECT.
>>>
>>> Jesper, thanks for your comments and very helpful discussion during
>>> NetConf! That's the plan, as we agreed. From our side I would like to
>>> reiterate again the importance of multi-buffer support by xdp frame.
>>> We would really prefer not to see our MTU shrinking because of xdp
>>> support.
>>
>> Okay we really need to make a serious attempt to find a way to support
>> multi-buffer packets with XDP. With the important criteria of not
>> hurting performance of the single-buffer per packet design.
>>
>> I've created a design document[2], that I will update based on our
>> discussions: [2]
>> https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
>>
>> The use-case that really convinced me was Eric's packet header-split.
>>
>>
>> Lets refresh: Why XDP don't have multi-buffer support:
>>
>> XDP is designed for maximum performance, which is why certain
>> driver-level
>> use-cases were not supported, like multi-buffer packets (like
>> jumbo-frames).
>> As it e.g. complicated the driver RX-loop and memory model handling.
>>
>> The single buffer per packet design, is also tied into eBPF
>> Direct-Access
>> (DA) to packet data, which can only be allowed if the packet memory is
>> in
>> contiguous memory. This DA feature is essential for XDP performance.
>>
>>
>> One way forward is to define that XDP only get access to the first
>> packet buffer, and it cannot see subsequent buffers. For XDP_TX and
>> XDP_REDIRECT to work then XDP still need to carry pointers (plus
>> len+offset) to the other buffers, which is 16 bytes per extra buffer.
>
>
> I’ve seen various network processor HW designs, and they normally get
> the first x bytes (128 - 512) which they can manipulate
> (append/prepend/insert/modify/delete).
>
> There are designs where they can “page in” the additional fragments
> but it’s expensive as it requires additional memory transfers. But the
> majority do not care (cannot change) the remaining fragments. Can also
> not think of a reason why you might want to remove something at the end
> of the frame (thinking about routing/forwarding needs here).
>
> If we do want XDP to access other fragments we could do this through a
> helper which swaps the packet context?
Yeah, I was also going to suggest a helper for that. It doesn't
necessarily need to swap the packet context, it could just return a new
pointer?
-Toke
next prev parent reply other threads:[~2019-06-28 7:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-23 7:06 [RFC V1 net-next 0/1] Introduce xdp to ena sameehj
2019-06-23 7:06 ` [RFC V1 net-next 1/1] net: ena: implement XDP drop support sameehj
2019-06-23 14:09 ` Jesper Dangaard Brouer
2019-06-23 14:21 ` Jesper Dangaard Brouer
2019-06-25 3:19 ` Machulsky, Zorik
2019-06-26 8:38 ` XDP multi-buffer incl. jumbo-frames (Was: [RFC V1 net-next 1/1] net: ena: implement XDP drop support) Jesper Dangaard Brouer
2019-06-26 11:52 ` Toke Høiland-Jørgensen
2019-06-26 14:40 ` Jesper Dangaard Brouer
2019-06-26 15:01 ` Toke Høiland-Jørgensen
2019-06-26 15:20 ` Willem de Bruijn
2019-06-26 16:42 ` Jonathan Lemon
2019-06-26 20:00 ` Jesper Dangaard Brouer
2019-06-27 22:07 ` Jonathan Lemon
2019-06-28 8:46 ` Jesper Dangaard Brouer
2019-06-26 15:14 ` Toke Høiland-Jørgensen
2019-06-26 16:36 ` Jesper Dangaard Brouer
2019-06-28 7:14 ` Eelco Chaudron
2019-06-28 7:46 ` Toke Høiland-Jørgensen [this message]
2019-06-28 11:49 ` Eelco Chaudron
2019-06-28 8:22 ` Jesper Dangaard Brouer
2019-06-23 14:28 ` [RFC V1 net-next 1/1] net: ena: implement XDP drop support David Ahern
2019-06-23 14:51 ` Maciej Fijalkowski
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