netdev - Re: RFC: Should net namespaces scale up (>10k) ?

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Message-ID: <CANn89i+kDvzWarnA4JJr2Cna2rCXrCFJjpmd7CNeVEj5tmtWMw@mail.gmail.com>
Date: Tue, 17 Sep 2024 08:59:05 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
Cc: Simon Horman <horms@...nel.org>, Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
	netdev@...r.kernel.org
Subject: Re: RFC: Should net namespaces scale up (>10k) ?

On Tue, Sep 17, 2024 at 12:06 AM Alexandre Ferrieux
<alexandre.ferrieux@...il.com> wrote:
>
> On 16/09/2024 16:01, Simon Horman wrote:
> >
> >> > Any insight on the (possibly very good) reasons those two apparent
> >> > warts stand in the way of netns scaling up ?
> >>
> >> I guess that the reason is more pragmatic, net namespaces are decade
> >> older than xarray, thus list-based implementation.
> >
> > Yes, I would also guess that the reason is not that these limitations were
> > part of the design. But just that the implementation scaled sufficiently at
> > the time. And that if further scale is required, then the implementation
> > can be updated.
>
> Okay, thank you for confirming my fears :}
> Now, what shall we do:
>
>  1. Ignore this corner case and carve the "few netns" assumption in stone;
>
>  2. Migrate netns IDs to xarrays (not to mention other leftover uses of IDR).
>
> Note that this funny workload of mine is a typical situation where the "DPDK
> beats Linux" myth gets reinforced. I find this pretty disappointing, as it
> implies reinventing the whole network stack in userspace. All the more so, as
> the other typical case for DPDK is now moot thanks to XDP.
>
> What do you think ?

I do not see any blocker for making things more scalable.

It is only a matter of time and interest. I think that 99.99 % of
linux hosts around the world
have less than 10 netns.

RTNL removal is a little bit harder (and we hit RTNL contention even
with less than 10 netns around)