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[146.241.235.217]) by smtp.gmail.com with ESMTPSA id d4-20020a05600c34c400b004155387c08esm2763782wmq.27.2024.04.11.08.59.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Apr 2024 08:59:01 -0700 (PDT) Message-ID: Subject: Re: [RFC] HW TX Rate Limiting Driver API From: Paolo Abeni To: Jakub Kicinski Cc: Simon Horman , netdev@vger.kernel.org, Jiri Pirko , Madhu Chittim , Sridhar Samudrala Date: Thu, 11 Apr 2024 17:58:59 +0200 In-Reply-To: <20240410075745.4637c537@kernel.org> References: <20240405102313.GA310894@kernel.org> <20240409153250.574369e4@kernel.org> <91451f2da3dcd70de3138975ad7d21f0548e19c9.camel@redhat.com> <20240410075745.4637c537@kernel.org> Autocrypt: addr=pabeni@redhat.com; prefer-encrypt=mutual; keydata=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 7ZxN9ZsDL38qVIuFkSpgMZCiUHdxBC11J8nbBSLlpnc924UAyr5XrGA99 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 iWjoCy8L35zPqR5TV+f5WR5hTVCqmLHSgm1jxwKhPg9L+GfuE4d0SWd84y GeOB3sSxlhWsuTj1K6K3MO9srD9hr0puqjO9sAizd0BJP8ucf/AACfrgmzIqZXCfVS7jJ/M+0ic+j1Si3yY8wYPEi3dvbVC0zsoGj9n1R7B7L9c3g1pZ4L9ui428vnPiMnDN3jh9OsdaXeWLvSvTylYvw9q0DEXVQTv4/OkcoMrfEkfbXbtZ3PRlAiddSZA5BDEkkm6P9KA2YAuooi1OD9d4MW8LFAeEicvHG+TPO6jtKTacdXDRe611EfRwTjBs19HmabSUfFcumL6BlVyceIoSqXFe5jOfGpbBevTZtg4kTSHqymGb6ra6sKs+/9aJiONs5NXY7iacZ55qG3Ib1cpQTps9bQILnqpwL2VTaH9TPGWwMY3Nc2VEc08zsLrXnA/yZKqZ1YzSY9MGXWYLkCDQRiEog1ARAAyXMKL+x1lDvLZVQjSUIVlaWswc0nV5y2EzBdbdZZCP3ysGC+s+n7xtq0o1wOvSvaG9h5q7sYZs+AKbuUbeZPu0bPWKoO02i00yVoSgWnEqDbyNeiSW+vI+VdiXITV83lG6pS+pAoTZlRROkpb5xo0gQ5ZeYok8MrkEmJbsPjdoKUJDBFTwrRnaDOfb+Qx1D22PlAZpdKiNtwbNZWiwEQFm6mHkIVSTUe2zSemoqYX4QQRvbmuMyPIbwbdNWlItukjHsffuPivLF/XsI1gDV67S1cVnQbBgrpFDxN62USwewXkNl+ndwa+15wgJFyq4Sd+RSMTPDzDQPFovyDfA/jxN2SK1Lizam6o+LBmvhIxwZOfdYH8bdYCoSpqcKLJVG3qVcTwbhGJr3kpRcBRz39Ml6iZhJyI3pEoX3bJTlR5Pr1Kjpx13qGydSMos94CIYWAKhegI06aTdvvuiigBwjngo/Rk5S+iEGR5KmTqGyp27o6YxZy6D4NIc6PKUzhIUxfvuHNvfu sD2W1U7eyLdm/jCgticGDsRtweytsgCSYfbz0gdgUuL3EBYN3JLbAU+UZpy 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2024-04-10 at 07:57 -0700, Jakub Kicinski wrote: > On Wed, 10 Apr 2024 10:33:50 +0200 Paolo Abeni wrote: > >=20 > > The reference to privileged functions is here to try to ensure proper > > isolation when required. > >=20 > > E.g. Let's suppose the admin in the the host wants to restricts/limits > > the B/W for a given VF (the VF itself, not the representor! See below > > WRT shaper_lookup_mode) to some rate, he/she likely wants intends > > additionally preventing the guest from relaxing the setting configuring > > the such rate on the guest device. >=20 > 1) representor is just a control path manifestation of the VF > any offload on the representor is for the VF - this is how forwarding > works, this is how "switchdev qdisc offload" works >=20 > 2) its a hierarchy, we can delegate one layer to the VF and the layer > under that to the eswitch manager. VF can set it limit to inf > but the eswitch layer should still enforce its limit > The driver implementation may constrain the number of layers, > delegation or form of the hierarchy, sure, but as I said, that's an > implementation limitation (which reminds me -- remember to add extack= =20 > to the "write" ops) >=20 > > > > enum shaper_lookup_mode { > > > > SHAPER_LOOKUP_BY_PORT, > > > > SHAPER_LOOKUP_BY_NETDEV, > > > > SHAPER_LOOKUP_BY_VF, > > > > SHAPER_LOOKUP_BY_QUEUE, > > > > SHAPER_LOOKUP_BY_TREE_ID, =20 > > >=20 > > > Two questions. > > >=20 > > > 1) are these looking up real nodes or some special kind of node which > > > can't have settings assigned directly?=C2=A0 > > > IOW if I want to rate limit=20 > > > the port do I get + set the port object or create a node above it and > > > link it up? =20 > >=20 > > There is no concept of such special kind of nodes. Probably the above > > enum needs a better/clearer definition of each element. > > How to reach a specific configuration for the port shaper depends on > > the NIC defaults - whatever hierarchy it provides/creates at > > initialization time.=C2=A0 > >=20 > > The NIC/firmware can either provide a default shaper for the port level > > - in such case the user/admin just need to set it. Otherwise user/admin > > will have to create the shaper and link it. >=20 > What's a default limit for a port? Line rate? > I understand that the scheduler can't be "disabled" but that doesn't mean > we must expose "noop" schedulers as if user has created them. >=20 > Let me step back. The goal, AFAIU, was to create an internal API into > which we can render existing APIs. We can combine settings from mqprio > and sysfs etc. and create a desired abstract hierarchy to present to=20 > the driver. That's doable. > Transforming arbitrary pre-existing driver hierarchy to achieve what > the uAPI wants.. would be an NP hard problem, no? >=20 > > I guess the first option should be more common/the expected one. > >=20 > > This proposal allows both cases. > >=20 > > > Or do those special nodes not exit implicitly (from the example it > > > seems like they do?) =20 >=20 > s/exit/exist/ > =20 > > Could you please re-phrase the above? >=20 > Basically whether dump of the hierarchy is empty at the start. >=20 > > > 2) the objects themselves seem rather different. I'm guessing we need > > > port/netdev/vf because either some users don't want to use switchdev > > > (vf =3D repr netdev) or drivers don't implement it "correctly" (port = !=3D > > > netdev?!)? =20 > >=20 > > Yes, the nodes inside the hierarchy can be linked to very different > > objects. The different lookup mode are there just to provide easy > > access to relevant objects. > >=20 > > Likely a much better description is needed: 'port' here is really the > > cable plug level, 'netdev' refers to the Linux network device. There > > could be multiple netdev for the same port as 'netdev' could be either > > referring to a PF or a VFs. Finally VF is really the virtual function > > device, not the representor, so that the host can configure/limits the > > guest tx rate.=20 > >=20 > > The same shaper can be reached/looked-up with different ids. > >=20 > > e.g. the device level shaper for a virtual function can be reached > > with: > >=20 > > - SHAPER_LOOKUP_BY_TREE_ID + unique tree id (every node is reachable > > this way) from any host device in the same hierarcy > > - SHAPER_LOOKUP_BY_VF + virtual function id, from the host PF device > > - SHAPER_LOOKUP_BY_NETDEV, from the guest VF device > >=20 > > > Also feels like some of these are root nodes, some are leaf nodes? = =20 > >=20 > > There is a single root node (the port's parent), possibly many internal > > nodes (port, netdev, vf, possibly more intermediate levels depending on > > the actual configuration [e.g. the firmware or the admin could create > > 'device groups' or 'queue groups']) and likely many leave nodes (queue > > level). > >=20 > > My personal take is than from an API point of view differentiating > > between leaves and internal nodes makes the API more complex with no > > practical advantage for the API users. >=20 > If you allow them to be configured. >=20 > What if we consider netdev/queue node as "exit points" of the tree,=20 > to which a layer of actual scheduling nodes can be attached, rather=20 > than doing scheduling by themselves? >=20 > > > > int (*get)(struct net_device *dev, > > > > enum shaper_lookup_mode lookup_mode, u32 id, > > > > struct shaper_info *shaper, struct netlink_ext_a= ck *extack); =20 > > >=20 > > > How about we store the hierarchy in the core? > > > Assume core has the source of truth, no need to get? =20 > >=20 > > One design choice was _not_ duplicating the hierarchy in the core: the > > full hierarchy is maintained only by the NIC/firmware.=C2=A0The NIC/fir= mware > > can perform some changes "automatically" e.g. when adding or deleting > > VFs or queues it will likely create/delete the paired shaper. The > > synchronization looks cumbersome and error prone. >=20 > The core only needs to maintain the hierarchy of whats in its domain of > control. >=20 > > The hierarchy could be exposed to both host and guests, I guess only > > the host core could be the source of truth, right? >=20 > I guess you're saying that the VF configuration may be implemented by ask= ing=20 > the PF driver to perform the actions? Perhaps we can let the driver alloc= ate > and maintain its own hierarchy but yes, we don't have much gain from hold= ing > that in the core. >=20 > This is the picture in my mind: >=20 > PF / eswitch domain >=20 > Q0 ]-> [50G] | RR | >-[ PF netdev =3D pf repr ] - | > Q1 ]-> [50G] | | | > | > ----------------------------------------- | > VF1 domain | | > | | > Q0 ]-> | RR | - [35G] >-[ VF netdev x vf repr ]-> [50G]- | RR | >- p= ort > Q1 ]-> | | | | > | | > ----------------------------------------- | > | > ------------------------------------------- | > VF2 domain | | > | | > Q0 ]-> [100G] -> |0 SP | >-[ VF net.. x vf r ]-> [50G] - | > Q1 ]-> [200G] -> |1 | | | > ------------------------------------------- >=20 > In this contrived example we have VF1 which limited itself to 35G. > VF2 limited each queue to 100G and 200G (ignored, eswitch limit is lower) > and set strict priority between queues. > PF limits each of its queues, and VFs to 50G, no rate limit on the port. >=20 > "x" means we cross domains, "=3D" purely splices one hierarchy with anoth= er. >=20 > The hierarchy for netdevs always starts with a queue and ends in a netdev= . > The hierarchy for eswitch has just netdevs at each end (hierarchy is > shared by all netdevs with the same switchdev id). >=20 > If the eswitch implementation is not capable of having a proper repr for = PFs > the PF queues feed directly into the port. >=20 > The final RR node may be implicit (if hierarchy has loose ends, the are > assumed to RR at the last possible point before egress). Let me try to wrap-up all the changes suggested above: - we need to clearly define the initial/default status (possibly no b/w limits and all the objects on the same level doing RR) - The hierarchy controlled by the API should shown only non default/user-configured nodes - We need to drop the references to privileged VFs. - The core should maintain the full status of the user-provided configuration changes (say, the 'delta' hierarchy ) Am I missing something? Also it's not 110% clear to me the implication of: > consider netdev/queue node as "exit points" of the tree,=20 > to which a layer of actual scheduling nodes can be attached could you please rephrase a bit? I have the feeling the the points above should not require significant changes to the API defined here, mainly more clear documentation, but I'll have a better look. Thanks! Paolo=20