netdev - Re: [PATCH net-next v2 0/3] net: introduce rps_default

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Message-ID: <20230130135221.3deeed6c@kernel.org>
Date:   Mon, 30 Jan 2023 13:52:21 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Saeed Mahameed <saeed@...nel.org>, netdev@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH net-next v2 0/3] net: introduce rps_default_mask

On Mon, 30 Jan 2023 10:25:34 +0100 Paolo Abeni wrote:
> Let me try for a moment to revive this old thread.
> 
> Tha series proposed a new sysctl know to implement a global/default rps
> mask applying to all the network devices as a way to simplify some RT
> setups. It has been rejected as the required task is doable in user-
> space.
> 
> Currently the orchestration infrastructure does that, setting the per
> device, per queue rps mask and CPU isolation.
> 
> The above leads to a side problem: when there are lot of netns/devices
> with several queues, even a reasonably optimized user-space solution
> takes a relevant amount of time to traverse the relevant sysfs dirs and
> do I/O on them. Overall the additional time required is very
> measurable, easily ranging in seconds.
> 
> The default_rps_mask would basically kill that overhead.
> 
> Is the above a suitable use case?

Alright, thanks for trying the user space fix.