linux-kernel - Re: [RFC net-next v3 6/7] net: devmem: pre-read requested rx queues during bind

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Message-ID: <20250815102025.202c42d3@kernel.org>
Date: Fri, 15 Aug 2025 10:20:25 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: <almasrymina@...gle.com>, <asml.silence@...il.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, <cratiu@...dia.com>,
 <tariqt@...dia.com>, <parav@...dia.com>, Christoph Hellwig
 <hch@...radead.org>, <netdev@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [RFC net-next v3 6/7] net: devmem: pre-read requested rx queues
 during bind

On Fri, 15 Aug 2025 14:03:47 +0300 Dragos Tatulea wrote:
> Instead of reading the requested rx queues after binding the buffer,
> read the rx queues in advance in a bitmap and iterate over them when
> needed.
> 
> This is a preparation for fetching the DMA device for each queue.
> 
> This patch has no functional changes.

Nice!

> +	rxq_bitmap = bitmap_alloc(netdev->num_rx_queues, GFP_KERNEL);

FWIW I think you can use num_real_rx_queues since we're holding
the instance lock which prevents it from changing?

But it's just bits so doesn't matter all that much.