On Tue 2018-11-06 21:27:11, Kieran Bingham wrote: > From: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx> > > 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
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