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[80.107.116.53]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36d2716c684sm2560176f8f.28.2024.08.08.10.22.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Aug 2024 10:22:42 -0700 (PDT) Date: Thu, 8 Aug 2024 19:22:39 +0200 From: Lorenzo Bianconi To: Alexander Lobakin Cc: Daniel Xu , Alexander Lobakin , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Larysa Zaremba , Michal Swiatkowski , Jesper Dangaard Brouer , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "toke@redhat.com" , Lorenzo Bianconi , David Miller , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jesse Brandeburg , John Fastabend , Yajun Deng , Willem de Bruijn , "bpf@vger.kernel.org" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, xdp-hints@xdp-project.net Subject: Re: [xdp-hints] Re: [PATCH RFC bpf-next 32/52] bpf, cpumap: switch to GRO from netif_receive_skb_list() Message-ID: References: <20220628194812.1453059-1-alexandr.lobakin@intel.com> <20220628194812.1453059-33-alexandr.lobakin@intel.com> <54aab7ec-80e9-44fd-8249-fe0cabda0393@intel.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="gWopvvUjnRev2ziB" Content-Disposition: inline In-Reply-To: <54aab7ec-80e9-44fd-8249-fe0cabda0393@intel.com> --gWopvvUjnRev2ziB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > From: Lorenzo Bianconi > Date: Thu, 8 Aug 2024 06:54:06 +0200 >=20 > >> Hi Alexander, > >> > >> On Tue, Jun 28, 2022, at 12:47 PM, Alexander Lobakin wrote: > >>> cpumap has its own BH context based on kthread. It has a sane batch > >>> size of 8 frames per one cycle. > >>> GRO can be used on its own, adjust cpumap calls to the > >>> upper stack to use GRO API instead of netif_receive_skb_list() which > >>> processes skbs by batches, but doesn't involve GRO layer at all. > >>> It is most beneficial when a NIC which frame come from is XDP > >>> generic metadata-enabled, but in plenty of tests GRO performs better > >>> than listed receiving even given that it has to calculate full frame > >>> checksums on CPU. > >>> As GRO passes the skbs to the upper stack in the batches of > >>> @gro_normal_batch, i.e. 8 by default, and @skb->dev point to the > >>> device where the frame comes from, it is enough to disable GRO > >>> netdev feature on it to completely restore the original behaviour: > >>> untouched frames will be being bulked and passed to the upper stack > >>> by 8, as it was with netif_receive_skb_list(). > >>> > >>> Signed-off-by: Alexander Lobakin > >>> --- > >>> kernel/bpf/cpumap.c | 43 ++++++++++++++++++++++++++++++++++++++----- > >>> 1 file changed, 38 insertions(+), 5 deletions(-) > >>> > >> > >> AFAICT the cpumap + GRO is a good standalone improvement. I think > >> cpumap is still missing this. >=20 > The only concern for having GRO in cpumap without metadata from the NIC > descriptor was that when the checksum status is missing, GRO calculates > the checksum on CPU, which is not really fast. > But I remember sometimes GRO was faster despite that. >=20 > >> > >> I have a production use case for this now. We want to do some intellig= ent > >> RX steering and I think GRO would help over list-ified receive in some= cases. > >> We would prefer steer in HW (and thus get existing GRO support) but no= t all > >> our NICs support it. So we need a software fallback. > >> > >> Are you still interested in merging the cpumap + GRO patches? >=20 > For sure I can revive this part. I was planning to get back to this > branch and pick patches which were not related to XDP hints and send > them separately. >=20 > >=20 > > Hi Daniel and Alex, > >=20 > > Recently I worked on a PoC to add GRO support to cpumap codebase: > > - https://github.com/LorenzoBianconi/bpf-next/commit/a4b8264d5000ecf016= da5a2dd9ac302deaf38b3e > > Here I added GRO support to cpumap through gro-cells. > > - https://github.com/LorenzoBianconi/bpf-next/commit/da6cb32a4674aa7240= 1c7414c9a8a0775ef41a55 > > Here I added GRO support to cpumap trough napi-threaded APIs (with a = some > > changes to them). >=20 > Hmm, when I was testing it, adding a whole NAPI to cpumap was sorta > overkill, that's why I separated GRO structure from &napi_struct. if we consider the NAPI-threaded implementation, we have the same architect= ure we have in current cpumap codebase, a thread for each cpumap entry, the only different is we can rely on GRO APIs. Regards, Lorenzo >=20 > Let me maybe find some free time, I would then test all 3 solutions > (mine, gro_cells, threaded NAPI) and pick/send the best? >=20 > >=20 > > Please note I have not run any performance tests so far, just verified = it does > > not crash (I was planning to resume this work soon). Please let me know= if it > > works for you. > >=20 > > Regards, > > Lorenzo > >=20 > >> > >> Thanks, > >> Daniel >=20 > Thanks, > Olek >=20 --gWopvvUjnRev2ziB Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCZrT+3AAKCRA6cBh0uS2t rNmOAQCJ9AZ6VVqlHeY+Ep7EQlMd0ybYpws3TIoQ8xaHVmjHyAD9HFXaElQMwHQ4 DACmDzL52jcn/Xv3bji9aj2oL+3shwg= =3Ltv -----END PGP SIGNATURE----- --gWopvvUjnRev2ziB--