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Date:   Sat, 27 Jul 2019 13:18:48 -0700 (PDT)
Message-Id: <20190727.131848.1034715270924665758.davem@davemloft.net>
To:     brodie.greenfield@alliedtelesis.co.nz
Cc:     stephen@networkplumber.org, kuznet@ms2.inr.ac.ru,
        yoshfuji@linux-ipv6.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, chris.packham@alliedtelesis.co.nz,
        luuk.paulussen@alliedtelesis.co.nz
Subject: Re: [PATCH 0/2] Make ipmr queue length configurable
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20190725204230.12229-1-brodie.greenfield@alliedtelesis.co.nz>
References: <20190725204230.12229-1-brodie.greenfield@alliedtelesis.co.nz>
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From: Brodie Greenfield <brodie.greenfield@alliedtelesis.co.nz>
Date: Fri, 26 Jul 2019 08:42:28 +1200

> We want to have some more space in our queue for processing incoming
> multicast packets, so we can process more of them without dropping
> them prematurely. It is useful to be able to increase this limit on
> higher-spec platforms that can handle more items.
> 
> For the particular use case here at Allied Telesis, we have linux
> running on our switches and routers, with support for the number of
> multicast groups being increased. Basically, this queue length affects
> the time taken to fully learn all of the multicast streams. 
> 
> Changes in v3:
>  - Corrected a v4 to v6 typo.

As others have voiced, I think it's dangerous to let every netns
increase this so readily.

We need to either put in a non-initns limit or simply not allow
non-init namespaces to change this.

But really socket queue limits are a better place to enforce this.