netdev - Re: [PATCH v3 net-next 0/3] net: Provide SMP threads for backlog NAPI

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Message-ID: <20240304193033.1c433585@kernel.org>
Date: Mon, 4 Mar 2024 19:30:33 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jesper Dangaard Brouer <hawk@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
 Wander Lairson Costa <wander@...hat.com>, Yan Zhai <yan@...udflare.com>
Subject: Re: [PATCH v3 net-next 0/3] net: Provide SMP threads for backlog
 NAPI

On Wed, 28 Feb 2024 13:05:47 +0100 Sebastian Andrzej Siewior wrote:
> The RPS code and "deferred skb free" both send IPI/ function call
> to a remote CPU in which a softirq is raised. This leads to a warning on
> PREEMPT_RT because raising softiqrs from function call led to undesired
> behaviour in the past. I had duct tape in RT for the "deferred skb free"
> and Wander Lairson Costa reported the RPS case.
> 
> This series only provides support for SMP threads for backlog NAPI, I
> did not attach a patch to make it default and remove the IPI related
> code to avoid confusion. I can post it for reference it asked.
> 
> The RedHat performance team was so kind to provide some testing here.
> The series (with the IPI code removed) has been tested and no regression
> vs without the series has been found. For testing iperf3 was used on 25G
> interface, provided by mlx5, ix40e or ice driver and RPS was enabled. I
> can provide the individual test results if needed.

Acked-by: Jakub Kicinski <kuba@...nel.org>