Re: [PATCH v5 0/9] Asynchronous UVC

[Pavel Machek <pavel@ucw.cz>]

[-- Attachment #1: Type: text/plain, Size: 1539 bytes --]

On Tue 2018-11-06 21:27:11, Kieran Bingham wrote:
> From: Kieran Bingham <kieran.bingham@ideasonboard.com>
> 
> The Linux UVC driver has long provided adequate performance capabilities for
> web-cams and low data rate video devices in Linux while resolutions were low.
> 
> Modern USB cameras are now capable of high data rates thanks to USB3 with
> 1080p, and even 4k capture resolutions supported.
> 
> Cameras such as the Stereolabs ZED (bulk transfers) or the Logitech BRIO
> (isochronous transfers) can generate more data than an embedded ARM core is
> able to process on a single core, resulting in frame loss.
> 
> A large part of this performance impact is from the requirement to
> ‘memcpy’ frames out from URB packets to destination frames. This unfortunate
> requirement is due to the UVC protocol allowing a variable length header, and
> thus it is not possible to provide the target frame buffers directly.
> 
> Extra throughput is possible by moving the actual memcpy actions to a work
> queue, and moving the memcpy out of interrupt context thus allowing work tasks
> to be scheduled across multiple cores.

Hmm. Doing memcpy() on many cores is improvement but... not really.
Would it be possible to improve kernel<->user interface, so it says
"data is in this buffer, and it starts here" and so that memcpy in
kernel is not neccessary?
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]