Hi Laurent, On Wed, Aug 8, 2018 at 8:12 AM Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > Hi Tomasz, > > On Tuesday, 7 August 2018 12:54:02 EEST Tomasz Figa wrote: > > On Wed, Mar 28, 2018 at 1:47 AM Kieran Bingham wrote: > > [snip] > > > In our testing, this function ends up being called twice > > In your testing, has this patch series brought noticeable performance > improvements ? Is there a particular reason you tested it, beside general > support of UVC devices in ChromeOS ? Some of our older ARM devices have external USB ports wired to a low end dwc2 controller, which puts quite strict timing requirements on interrupt handling. For some cameras that produce bigger payloads (in our testing that was Logitech BRIO, running at 1080p), almost half of every frame would be dropped, due to the memcpy from uncached memory taking too much time. With this series, it goes down to bottom ~10% of only a part of the frames. With one more optimization from Keiichi [1], the problem disappears almost completely. [1] https://lore.kernel.org/patchwork/patch/956388/ Best regards, Tomasz
