Keith Whitwell wrote: > This seems wrong to me -- the client doesn't need to sleep - all it's going > to do is build a command buffer targeting the new backbuffer. There's no > problem with that, it should be the preserve of the GPU scheduler (TTM or > GEM) to ensure those commands (once submitted) don't get executed until the > buffer is available - otherwise you're potentially pausing your application > for no good reason. The app should be throttled if it gets more than a > couple of frames ahead, but there should be 100% overlap with hardware > otherwise. > > If you need a solution that doesn't rely on the buffer manager, perhaps > resort to triple-buffering, or else create a new buffer and return that in > DRI2GetBuffers (and let the scanout one be freed once the flip is done). > > It seems like arbitrating command execution against on-hardware buffers > should be the preserve of the kernel memory manager & other actors shouldn't > be double-guessing that. > I agree.
It would be fairly trivial to use TTMs synchronization mechanisms to put special fences on buffers with outstanding flips. These fences signal when a "software flipper" engine has programmed a flip. Any command submission involving these buffers while fenced will effectively put the rendering client to sleep. Rendering to other buffers, including a potential third buffer would continue undisturbed. Pinning and unpinning of scanouts would take place at command submission time as detailed before. Of course, in the case of AIGLX, the X server might temporarily be put to sleep, which might not be fully optimal. A "software flipper" engine would be a simple vblank irq handler that flips and signals the flipper fence when the previous fences of the buffers (if present) have signaled (to finish any outstanding rendering before flipping). I guess GEM's buffer object busy lists be used to accomodate something similar? /Thomas > Keith > ________________________________________ > From: Kristian Høgsberg [...@bitplanet.net] > Sent: Tuesday, August 18, 2009 11:46 AM > To: Thomas Hellström > Cc: Kristian Høgsberg; Jesse Barnes; dri-de...@lists.sf.net > Subject: Re: [PATCH] Add modesetting pageflip ioctl and corresponding drm > event > > We don't put clients to sleep until they try to render to the new > backbuffer. For direct rendering this happens when the client calls > DRI2GetBuffers() after having called DRI2SwapBuffers(). If the flip > is not yet finished at that time, we restart the X request and suspend > the client. When the drm event fires it is read by the ddx driver, > which then calls DRI2SwapComplete() which will wake the client up > again. For AIGLX, we suspend the client in __glXForceCurrent(), but > the wakeup happens the same way. > ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
