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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Stanislav Fomichev <sdf@google.com>, bpf <bpf@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>, Saeed Mahameed <saeedm@nvidia.com>,
	David Ahern <dsahern@gmail.com>, Jakub Kicinski <kuba@kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Anatoly Burakov <anatoly.burakov@intel.com>,
	Alexander Lobakin <alexandr.lobakin@intel.com>,
	Magnus Karlsson <magnus.karlsson@gmail.com>,
	Maryam Tahhan <mtahhan@redhat.com>,
	xdp-hints@xdp-project.net,
	Network Development <netdev@vger.kernel.org>
Subject: [xdp-hints] Re: [PATCH bpf-next v3 11/12] mlx5: Support RX XDP metadata
Date: Fri, 09 Dec 2022 01:29:16 +0100	[thread overview]
Message-ID: <87tu25ju77.fsf@toke.dk> (raw)
In-Reply-To: <CAADnVQ+=71Y+ypQTOgFTJWY7w3YOUdY39is4vpo3aou11=eMmw@mail.gmail.com>

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> On Thu, Dec 8, 2022 at 4:02 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> Stanislav Fomichev <sdf@google.com> writes:
>>
>> > On Thu, Dec 8, 2022 at 2:59 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>> >>
>> >> Stanislav Fomichev <sdf@google.com> writes:
>> >>
>> >> > From: Toke Høiland-Jørgensen <toke@redhat.com>
>> >> >
>> >> > Support RX hash and timestamp metadata kfuncs. We need to pass in the cqe
>> >> > pointer to the mlx5e_skb_from* functions so it can be retrieved from the
>> >> > XDP ctx to do this.
>> >>
>> >> So I finally managed to get enough ducks in row to actually benchmark
>> >> this. With the caveat that I suddenly can't get the timestamp support to
>> >> work (it was working in an earlier version, but now
>> >> timestamp_supported() just returns false). I'm not sure if this is an
>> >> issue with the enablement patch, or if I just haven't gotten the
>> >> hardware configured properly. I'll investigate some more, but figured
>> >> I'd post these results now:
>> >>
>> >> Baseline XDP_DROP:         25,678,262 pps / 38.94 ns/pkt
>> >> XDP_DROP + read metadata:  23,924,109 pps / 41.80 ns/pkt
>> >> Overhead:                   1,754,153 pps /  2.86 ns/pkt
>> >>
>> >> As per the above, this is with calling three kfuncs/pkt
>> >> (metadata_supported(), rx_hash_supported() and rx_hash()). So that's
>> >> ~0.95 ns per function call, which is a bit less, but not far off from
>> >> the ~1.2 ns that I'm used to. The tests where I accidentally called the
>> >> default kfuncs cut off ~1.3 ns for one less kfunc call, so it's
>> >> definitely in that ballpark.
>> >>
>> >> I'm not doing anything with the data, just reading it into an on-stack
>> >> buffer, so this is the smallest possible delta from just getting the
>> >> data out of the driver. I did confirm that the call instructions are
>> >> still in the BPF program bytecode when it's dumped back out from the
>> >> kernel.
>> >>
>> >> -Toke
>> >>
>> >
>> > Oh, that's great, thanks for running the numbers! Will definitely
>> > reference them in v4!
>> > Presumably, we should be able to at least unroll most of the
>> > _supported callbacks if we want, they should be relatively easy; but
>> > the numbers look fine as is?
>>
>> Well, this is for one (and a half) piece of metadata. If we extrapolate
>> it adds up quickly. Say we add csum and vlan tags, say, and maybe
>> another callback to get the type of hash (l3/l4). Those would probably
>> be relevant for most packets in a fairly common setup. Extrapolating
>> from the ~1 ns/call figure, that's 8 ns/pkt, which is 20% of the
>> baseline of 39 ns.
>>
>> So in that sense I still think unrolling makes sense. At least for the
>> _supported() calls, as eating a whole function call just for that is
>> probably a bit much (which I think was also Jakub's point in a sibling
>> thread somewhere).
>
> imo the overhead is tiny enough that we can wait until
> generic 'kfunc inlining' infra is ready.
>
> We're planning to dual-compile some_kernel_file.c
> into native arch and into bpf arch.
> Then the verifier will automatically inline bpf asm
> of corresponding kfunc.

Is that "planning" or "actively working on"? Just trying to get a sense
of the time frames here, as this sounds neat, but also something that
could potentially require quite a bit of fiddling with the build system
to get to work? :)

-Toke


  reply	other threads:[~2022-12-09  0:29 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-06  2:45 [xdp-hints] [PATCH bpf-next v3 00/12] xdp: hints via kfuncs Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 01/12] bpf: Document XDP RX metadata Stanislav Fomichev
2022-12-08  4:25   ` [xdp-hints] " Jakub Kicinski
2022-12-08 19:06     ` Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 02/12] bpf: Rename bpf_{prog,map}_is_dev_bound to is_offloaded Stanislav Fomichev
2022-12-08  4:26   ` [xdp-hints] " Jakub Kicinski
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 03/12] bpf: XDP metadata RX kfuncs Stanislav Fomichev
2022-12-07  4:29   ` [xdp-hints] " Alexei Starovoitov
2022-12-07  4:52     ` Stanislav Fomichev
2022-12-07  7:23       ` Martin KaFai Lau
2022-12-07 18:05         ` Stanislav Fomichev
2022-12-08  2:47   ` Martin KaFai Lau
2022-12-08 19:07     ` Stanislav Fomichev
2022-12-08 22:53       ` Martin KaFai Lau
2022-12-08 23:45         ` Stanislav Fomichev
2022-12-08  5:00   ` Jakub Kicinski
2022-12-08 19:07     ` Stanislav Fomichev
2022-12-09  1:30       ` Jakub Kicinski
2022-12-09  2:57         ` Stanislav Fomichev
2022-12-08 22:39   ` Toke Høiland-Jørgensen
2022-12-08 23:46     ` Stanislav Fomichev
2022-12-09  0:07       ` Toke Høiland-Jørgensen
2022-12-09  2:57         ` Stanislav Fomichev
2022-12-10  0:42           ` Martin KaFai Lau
2022-12-10  1:12             ` Martin KaFai Lau
2022-12-09 11:10   ` Jesper Dangaard Brouer
2022-12-09 17:47     ` Stanislav Fomichev
2022-12-11 11:09       ` Jesper Dangaard Brouer
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 04/12] veth: Introduce veth_xdp_buff wrapper for xdp_buff Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 05/12] veth: Support RX XDP metadata Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 06/12] selftests/bpf: Verify xdp_metadata xdp->af_xdp path Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 07/12] mlx4: Introduce mlx4_xdp_buff wrapper for xdp_buff Stanislav Fomichev
2022-12-08  6:11   ` [xdp-hints] " Tariq Toukan
2022-12-08 19:07     ` Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 08/12] mxl4: Support RX XDP metadata Stanislav Fomichev
2022-12-08  6:09   ` [xdp-hints] " Tariq Toukan
2022-12-08 19:07     ` Stanislav Fomichev
2022-12-08 20:23       ` Tariq Toukan
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 09/12] xsk: Add cb area to struct xdp_buff_xsk Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 10/12] mlx5: Introduce mlx5_xdp_buff wrapper for xdp_buff Stanislav Fomichev
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 11/12] mlx5: Support RX XDP metadata Stanislav Fomichev
2022-12-08 22:59   ` [xdp-hints] " Toke Høiland-Jørgensen
2022-12-08 23:45     ` Stanislav Fomichev
2022-12-09  0:02       ` Toke Høiland-Jørgensen
2022-12-09  0:07         ` Alexei Starovoitov
2022-12-09  0:29           ` Toke Høiland-Jørgensen [this message]
2022-12-09  0:32             ` Alexei Starovoitov
2022-12-09  0:53               ` Toke Høiland-Jørgensen
2022-12-09  2:57                 ` Stanislav Fomichev
2022-12-09  5:24                   ` Saeed Mahameed
2022-12-09 12:59                     ` Jesper Dangaard Brouer
2022-12-09 14:37                       ` Toke Høiland-Jørgensen
2022-12-09 15:19                       ` Dave Taht
2022-12-09 14:42                   ` Toke Høiland-Jørgensen
2022-12-09 16:45                     ` Jakub Kicinski
2022-12-09 17:46                       ` Stanislav Fomichev
2022-12-09 22:13                         ` Jakub Kicinski
2022-12-06  2:45 ` [xdp-hints] [PATCH bpf-next v3 12/12] selftests/bpf: Simple program to dump XDP RX metadata Stanislav Fomichev
2022-12-08 22:28 ` [xdp-hints] Re: [PATCH bpf-next v3 00/12] xdp: hints via kfuncs Toke Høiland-Jørgensen
2022-12-08 23:47   ` Stanislav Fomichev
2022-12-09  0:14     ` Toke Høiland-Jørgensen

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