netdev - Re: [PATCH v2 3/5] can: esd_usb: Add watermark handling for TX jobs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250919-impressive-pillbug-of-diversity-832227-mkl@pengutronix.de>
Date: Fri, 19 Sep 2025 19:49:35 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Stefan Mätje <stefan.maetje@....eu>
Cc: Vincent Mailhol <mailhol@...nel.org>, 
	Frank Jungclaus <frank.jungclaus@....eu>, linux-can@...r.kernel.org, socketcan@....eu, 
	Simon Horman <horms@...nel.org>, Oliver Hartkopp <socketcan@...tkopp.net>, 
	Wolfgang Grandegger <wg@...ndegger.com>, "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 3/5] can: esd_usb: Add watermark handling for TX jobs

On 21.08.2025 16:34:20, 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.

Just came into my mind:

In a future patch you can make the watermark dependent on the actual USB
device and or the USB connection type.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)