netdev - Re: [PATCH v3 03/12] net-shapers: implement NL get operation

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Message-ID: <b75dfc17-303a-4b91-bd16-5580feefe177@redhat.com>
Date: Tue, 13 Aug 2024 17:17:12 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
 Madhu Chittim <madhu.chittim@...el.com>,
 Sridhar Samudrala <sridhar.samudrala@...el.com>,
 Simon Horman <horms@...nel.org>, John Fastabend <john.fastabend@...il.com>,
 Sunil Kovvuri Goutham <sgoutham@...vell.com>,
 Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH v3 03/12] net-shapers: implement NL get operation

On 8/1/24 15:42, Jiri Pirko wrote:
> Tue, Jul 30, 2024 at 10:39:46PM CEST, pabeni@...hat.com wrote:
>> +/**
>> + * net_shaper_make_handle - creates an unique shaper identifier
>> + * @scope: the shaper scope
>> + * @id: the shaper id number
>> + *
>> + * Return: an unique identifier for the shaper
>> + *
>> + * Combines the specified arguments to create an unique identifier for
>> + * the shaper. The @id argument semantic depends on the
>> + * specified scope.
>> + * For @NET_SHAPER_SCOPE_QUEUE_GROUP, @id is the queue group id
>> + * For @NET_SHAPER_SCOPE_QUEUE, @id is the queue number.
>> + * For @NET_SHAPER_SCOPE_VF, @id is virtual function number.
>> + */
>> +static inline u32 net_shaper_make_handle(enum net_shaper_scope scope,
>> +					 int id)
>> +{
>> +	return FIELD_PREP(NET_SHAPER_SCOPE_MASK, scope) |
>> +		FIELD_PREP(NET_SHAPER_ID_MASK, id);
> 
> Perhaps some scopes may find only part of u32 as limitting for id in
> the future? I find it elegant to have it in single u32 though. u64 may
> be nicer (I know, xarray) :)

With this code the id limit is 2^26 for each scope. The most capable H/W 
I'm aware of supports at most 64K shapers, overall. Are you aware of any 
specific constraint we need to address?

[...]
>> int net_shaper_nl_get_doit(struct sk_buff *skb, struct genl_info *info)
>> {
>> -	return -EOPNOTSUPP;
>> +	struct net_shaper_info *shaper;
>> +	struct net_device *dev;
>> +	struct sk_buff *msg;
>> +	u32 handle;
>> +	int ret;
>> +
>> +	ret = fetch_dev(info, &dev);
> 
> This is quite net_device centric. Devlink rate shaper should be
> eventually visible throught this api as well, won't they? How do you
> imagine that?

I'm unsure we are on the same page. Do you foresee this to replace and 
obsoleted the existing devlink rate API? It was not our so far.

> Could we have various types of binding? Something like:
> 
> NET_SHAPER_A_BINDING nest
>    NET_SHAPER_A_BINDING_IFINDEX u32
> 
> or:
> NET_SHAPER_A_BINDING nest
>    NET_SHAPER_A_BINDING_DEVLINK_PORT nest
>      DEVLINK_ATTR_BUS_NAME string
>      DEVLINK_ATTR_DEV_NAME string
>      DEVLINK_ATTR_PORT_INDEX u32
> 
> ?

Somewhat related, the current get()/dump() operations currently don't 
return the shaper ifindex. I guess we can include 'scope' and 'id' under 
NET_SHAPER_A_BINDING and replace the existing handle attribute with it.

It should cover eventual future devlink extensions and provide all the 
relevant info for get/dump sake.

>> +
>> static int __init shaper_init(void)
> 
> 
> 
> fetch_dev
> fill_handle
> parse_handle
> sc_lookup
> __sc_container
> dev_shaper_flush
> shaper_init
> 
> 
> Could you perhaps maintain net_shaper_ prefix for all of there?

Most of the helpers are static and should never be visible outside this 
compilation unit, so I did not bother with a prefix, I'll add it in the 
next revision.

Thanks,

Paolo