On Thu, Sep 9, 2021 at 9:16 AM Simon Ser contact@emersion.fr wrote:

Out of curiosity, would it be reasonable to allow user-space (more precisely, the compositor) to set the deadline via an IOCTL without actually performing an atomic commit with the FB?

Some compositors might want to wait themselves for FB fence completions to ensure a client doesn't block the whole desktop (by submitting a very costly rendering job). In this case it would make sense for the compositor to indicate that it intends to display the buffer on next vblank if it's ready by that point, without queueing a page-flip yet.

Yes, I think it would.. and "dma-buf/sync_file: Add SET_DEADLINE ioctl" adds such an ioctl.. just for the benefit of igt tests at this point, but the thought was it would be also used by compositors that are doing such frame scheduling. Ofc danvet is a bit grumpy that there isn't a more real (than igt) userspace for the ioctl yet ;-)

BR, -R