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Date: Fri, 26 Sep 2014 13:15:10 -0600
From: David Ahern <lxhacker68@gmail.com>
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To: nicolas.dichtel@6wind.com, Cong Wang <cwang@twopensource.com>
CC: netdev <netdev@vger.kernel.org>, containers@lists.linux-foundation.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-api@vger.kernel.org, David Miller <davem@davemloft.net>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>
Subject: Re: [RFC PATCH net-next v2 0/5] netns: allow to identify peer netns
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On 9/26/14, 7:40 AM, Nicolas Dichtel wrote:
>>
>>
>> No, I don't want to monitor anything. Even if I wanted, I would just
>> start one
>> daemon in each netns instead of one for all.
> Ok you don't want, but some other people (not only me) want it! And
> having one
> daemon per netns does not scale: there are scenarii with thousand netns
> which
> are dynamically created and deleted.

An example of the scaling problem using quagga (old but still seems to 
be a relevant data point):

 
https://lists.quagga.net/pipermail/quagga-users/2010-February/011351.html

"2k VRFs that would be 2.6G"

And that does not include the overhead of each namespace -- roughly 
200kB/namespace on one kernel I checked (v3.10). So that's a ballpark of 
3G of memory.

David