netdev - Re: [PATCH 4/6] can: esd_usb: Add watermark handling for TX jobs

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Message-ID: <20250813-chubby-lizard-from-asgard-fb7867-mkl@pengutronix.de>
Date: Wed, 13 Aug 2025 10:13:25 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Stefan Mätje <stefan.maetje@....eu>
Cc: Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
	Frank Jungclaus <frank.jungclaus@....eu>, linux-can@...r.kernel.org, socketcan@....eu, 
	Simon Horman <horms@...nel.org>, Olivier Sobrie <olivier@...rie.be>, 
	Oliver Hartkopp <socketcan@...tkopp.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 4/6] can: esd_usb: Add watermark handling for TX jobs

On 11.08.2025 23:06:09, Stefan Mätje wrote:
> The driver tried to keep as much CAN frames as possible submitted to the
> USB device (ESD_USB_MAX_TX_URBS). This has led to occasional "No free
> context" error messages in high load situations like with
> "cangen -g 0 -p 10 canX".
> 
> This patch now calls netif_stop_queue() already if the number of active
> jobs reaches ESD_USB_TX_URBS_HI_WM which is < ESD_USB_MAX_TX_URBS.
> The netif_start_queue() is called in esd_usb_tx_done_msg() only if
> the number of active jobs is <= ESD_USB_TX_URBS_LO_WM.
> 
> This change eliminates the occasional error messages and significantly
> reduces the number of calls to netif_start_queue() and
> netif_stop_queue().
> 
> The watermark limits have been chosen with the CAN-USB/Micro in mind to
> not to compromise its TX throughput. This device is running on USB 1.1
> only with its 1ms USB polling cycle where a ESD_USB_TX_URBS_LO_WM
> value below 9 decreases the TX throughput.
> 
> Signed-off-by: Stefan Mätje <stefan.maetje@....eu>

Please add a Fixes tag.

Marc

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