netdev - Re: [PATCH v3 net-next 2/4] net: dsa: Link aggregation support

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Message-ID: <87mtyw7a6w.fsf@waldekranz.com>
Date:   Wed, 02 Dec 2020 11:51:19 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        j.vosburgh@...il.com, vfalico@...il.com, andy@...yhouse.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next 2/4] net: dsa: Link aggregation support

On Wed, Dec 02, 2020 at 12:07, Vladimir Oltean <olteanv@...il.com> wrote:
> On Wed, Dec 02, 2020 at 10:13:54AM +0100, Tobias Waldekranz wrote:
>> +
>> +	/* Link aggregates */
>> +	struct {
>> +		struct dsa_lag *pool;
>> +		unsigned long *busy;
>> +		unsigned int num;
>
> Can we get rid of the busy array and just look at the refcounts?

We can, but it is typically 4/8B that makes iterating over used LAGs,
finding the first free LAG etc. much easier.

> Can we also get rid of the "num" variable?

It can be computed but it requires traversing the entire dst port list
every time, as you can see in dsa_tree_setup_lags. We need to hoist the
lowest supported num up from the ds level to the dst.