netdev - Re: [PATCH net-next v2] gtp: add notification mechanism

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Message-ID: <20200826185202.GZ3739@nataraja>
Date:   Wed, 26 Aug 2020 20:52:02 +0200
From:   Harald Welte <laforge@...monks.org>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     netdev@...r.kernel.org, osmocom-net-gprs@...ts.osmocom.org,
        Gabriel Ganne <gabriel.ganne@...nd.com>, kuba@...nel.org,
        davem@...emloft.net, pablo@...filter.org
Subject: Re: [PATCH net-next v2] gtp: add notification mechanism

Hi Nicolas,

On Wed, Aug 26, 2020 at 09:47:54AM +0200, Nicolas Dichtel wrote:
> > Sending (unsolicited) notifications about all of those seems quite heavyweight to me.
>
> There is no 'unsolicited' notifications with this patch. Notifications are sent
> only if a userspace application has subscribed to the gtp mcast group.
> ip routes or conntrack entries are notified in the same way and there could a
> lot of them also (more than 100k conntrack entries for example).

Ok, thanks for reminding me of that.  However, even if those events are
not sent/multicasted, it still looks like the proposed patch is
unconditionally allocating a netlink message and filling it with
information about the PDP.  That alone looks like adding significant
overhead to every user - even the majority of current use cases where
nobody is listening/subscribing to that multicast group.

Wouldn't it make sense to only allocate + fill those messages if we
actually knew a subscriber existed?

-- 
- Harald Welte <laforge@...monks.org>           http://laforge.gnumonks.org/
============================================================================
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