On Thu, Nov 15, 2012 at 3:30 PM, Michel Dänzer <mic...@daenzer.net> wrote: > On Don, 2012-11-15 at 04:43 +0100, Marek Olšák wrote: >> >> For the asynchronous SwapBuffers to work, there must be a separate X >> connection, because Xlib isn't thread-safe at all. >> >> Now the bad news. The DRI invalidate events may be received too late. >> We can't wait for the events in glXSwapBuffers, because that would >> defeat the whole purpose of thread offloading. > > Why would it? Couldn't you e.g. have the main thread wait for the > SwapBuffers thread to get the events when it needs the buffer > information for the next frame?
The problem is I have to flush the context first, which calls the CS ioctl and sysprof shows it usually takes about 20% of all CPU time if that is the only context flush in the whole frame. If I flush the context in the driver thread and at the same time I swap the buffers in the main thread, the buffers may be swapped before the context is fully flushed and an incomplete frame is displayed. So the context must be flushed *before* the swapping. Then we can swap the buffers, process all the events (XSync) and get the swap-buffers reply. This all must be done in the driver thread for it to work. If I can't offload the swapping, I can't offload the context flush either (unless the kernel can somehow synchronize the two, even though they are parallel in userspace). > > >> For normal apps, that only happens when the window is resized, so only >> the next rendered frame is likely to contain garbage. > > DRI2SwapBuffers also generates invalidate events, and those can be > crucial e.g. with page flipping. DRI2SwapBuffers is gone, see: http://www.mail-archive.com/mesa-dev@lists.freedesktop.org/msg27459.html All I am talking about is offloading the dri2SwapBuffers call (flush+swap) in glx/dri2_glx.c. > > >> Compositors don't work very well with this. I think it's because of >> the invalidate events not being received in time. As a temporary >> solution, I turn off asynchronous SwapBuffers if dri2_bind_tex_image >> is called, which should cover all compositors that either directly or >> indirectly use GLX. > > I fail to see the connection. Maybe the compositors break because they > use page flipping, per above? I have SwapBuffersWait turned off, which also turns off page flipping AFAIK. I guess I could try to invalidate all drawables before SwapBuffers if that's even possible. Marek _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
