netdev - Re: [PATCH v2 1/5] ethernet: add sun8i-emac driver

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Date:	Wed, 20 Jul 2016 11:56:12 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	LABBE Corentin <clabbe.montjoie@...il.com>, robh+dt@...nel.org,
	mark.rutland@....com, maxime.ripard@...e-electrons.com,
	wens@...e.org, linux@...linux.org.uk, davem@...emloft.net,
	devicetree@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v2 1/5] ethernet: add sun8i-emac driver

On Wednesday, July 20, 2016 10:03:16 AM CEST LABBE Corentin wrote:
> +
> +       /* Benched on OPIPC with 100M, setting more than 256 does not give any
> +        * perf boost
> +        */
> +       priv->nbdesc_rx = 128;
> +       priv->nbdesc_tx = 256;
> +
> 

256 tx descriptors can introduce a significant latency. Can you add
support for BQL (netdev_sent_queue/netdev_completed_queue) to limit
the queue size to the minimum?

I also noticed that your tx_lock() prevents you from concurrently
running sun8i_emac_complete_xmit() and sun8i_emac_xmit(). Is that
necessary? I'd think that you can find a way to make them work
concurrently.

	Arnd