netdev - Re: [PATCH net-next v2] net/core: add optional threading for backlog processing

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Message-ID: <20230328161642.3d2f101c@kernel.org>
Date:   Tue, 28 Mar 2023 16:16:42 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Felix Fietkau <nbd@....name>
Cc:     netdev@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] net/core: add optional threading for
 backlog processing

On Tue, 28 Mar 2023 21:59:25 +0200 Felix Fietkau wrote:
> When dealing with few flows or an imbalance on CPU utilization, static RPS
> CPU assignment can be too inflexible. Add support for enabling threaded NAPI
> for backlog processing in order to allow the scheduler to better balance
> processing. This helps better spread the load across idle CPUs.

Can you share some numbers vs a system where RPS only spreads to 
the cores which are not running NAPI?

IMHO you're putting a lot of faith in the scheduler and you need 
to show that it actually does what you say it will do.