netdev - Re: [RFC PATCH] net: introduce HW Rate Limiting Driver API

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Message-ID: <ZqjYKXLmeriWbYyC@nanopsycho.orion>
Date: Tue, 30 Jul 2024 14:10:17 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Cosmin Ratiu <cratiu@...dia.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"jhs@...atatu.com" <jhs@...atatu.com>,
	"sridhar.samudrala@...el.com" <sridhar.samudrala@...el.com>,
	"john.fastabend@...il.com" <john.fastabend@...il.com>,
	"madhu.chittim@...el.com" <madhu.chittim@...el.com>,
	"horms@...nel.org" <horms@...nel.org>,
	"sgoutham@...vell.com" <sgoutham@...vell.com>,
	"kuba@...nel.org" <kuba@...nel.org>
Subject: Re: [RFC PATCH] net: introduce HW Rate Limiting Driver API

Wed, Jun 05, 2024 at 05:52:32PM CEST, pabeni@...hat.com wrote:
>On Wed, 2024-06-05 at 15:04 +0000, Cosmin Ratiu wrote:
>> On Wed, 2024-05-08 at 22:20 +0200, Paolo Abeni wrote:
>> 
>> > +/**
>> > + * struct net_shaper_info - represents a shaping node on the NIC H/W
>> > + * @metric: Specify if the bw limits refers to PPS or BPS
>> > + * @bw_min: Minimum guaranteed rate for this shaper
>> > + * @bw_max: Maximum peak bw allowed for this shaper
>> > + * @burst: Maximum burst for the peek rate of this shaper
>> > + * @priority: Scheduling priority for this shaper
>> > + * @weight: Scheduling weight for this shaper
>> > + */
>> > +struct net_shaper_info {
>> > +	enum net_shaper_metric metric;
>> > +	u64 bw_min;	/* minimum guaranteed bandwidth, according to metric */
>> > +	u64 bw_max;	/* maximum allowed bandwidth */
>> > +	u32 burst;	/* maximum burst in bytes for bw_max */
>> 
>> 'burst' really should be u64 if it can deal with bytes. In a 400Gbps
>> link, u32 really is peanuts.
>> 
>> > +/**
>> > + * enum net_shaper_scope - the different scopes where a shaper could be attached
>> > + * @NET_SHAPER_SCOPE_PORT:   The root shaper for the whole H/W.
>> > + * @NET_SHAPER_SCOPE_NETDEV: The main shaper for the given network device.
>> > + * @NET_SHAPER_SCOPE_VF:     The shaper is attached to the given virtual
>> > + * function.
>> > + * @NET_SHAPER_SCOPE_QUEUE_GROUP: The shaper groups multiple queues under the
>> > + * same device.
>> > + * @NET_SHAPER_SCOPE_QUEUE:  The shaper is attached to the given device queue.
>> > + *
>> > + * NET_SHAPER_SCOPE_PORT and NET_SHAPER_SCOPE_VF are only available on
>> > + * PF devices, usually inside the host/hypervisor.
>> > + * NET_SHAPER_SCOPE_NETDEV, NET_SHAPER_SCOPE_QUEUE_GROUP and
>> > + * NET_SHAPER_SCOPE_QUEUE are available on both PFs and VFs devices.
>> > + */
>> > +enum net_shaper_scope {
>> > +	NET_SHAPER_SCOPE_PORT,
>> > +	NET_SHAPER_SCOPE_NETDEV,
>> > +	NET_SHAPER_SCOPE_VF,
>> > +	NET_SHAPER_SCOPE_QUEUE_GROUP,
>> > +	NET_SHAPER_SCOPE_QUEUE,
>> > +};
>> 
>> How would modelling groups of VFs (as implemented in [1]) look like
>> with this proposal?
>> I could imagine a NET_SHAPER_SCOPE_VF_GROUP scope, with a shared shaper
>> across multiple VFs. 
>
>Following-up yday reviewer mtg - which was spent mainly on this topic -
>- the current direction is to replace NET_SHAPER_SCOPE_QUEUE_GROUP with
>a more generic 'scope', grouping of either queues, VF/netdev or even
>other groups (allowing nesting).
>
>> How would managing membership of VFs in a group
>> look like? Will the devlink API continue to be used for that? Or will
>> something else be introduced?
>
>The idea is to introduce a new generic netlink interface, yaml-based,
>to expose these features to user-space.
>
>> Looking a bit into the future now...
>> I am nowadays thinking about extending the mlx5 VF group rate limit
>> feature to support VFs from multiple PFs from the same NIC (the
>> hardware can be configured to use a shared shaper across multiple
>> ports), how could that feature be represented in this API, given that
>> ops relate to a netdevice? Which netdevice should be used for this
>> scenario?
>
>I must admit we[1] haven't thought yet about the scenario you describe
>above. I guess we could encode the PF number and the VF number in the
>handle major/minor and operate on any PF device belonging to the same
>silicon, WDYT?

Sometimes, there is no netdevice at all. The infra still should work I
believe.


>
>Thanks,
>
>Paolo
>
>[1] or at least myself;)
>