Am Montag, den 07.02.2005, 09:20 +0000 schrieb Keith Whitwell: > > btw texdown showed that texture transfers to card memory are faster than > > to AGP memory, but not by very much (something like 100MB/s vs. 140MB/s > > in the best case, though the numbers I got fluctuated quite a bit). > > How are AGP texture uploads being done? > > The card memory uploads are actually done via agp buffers - ie the data > is written by the driver to agp memory, the card then copies that to > card memory. If the AGP case is the same, the data probably travels up > to the card and then back down again to AGP memory, accounting for the > relative slowdown. > > One benefit of using the card to do the up/downloads is synchronization > with the graphics engine - if you were to write the texture data > directly you'd have to have some extra mechanisms to ensure that the > memory wasn't being used by commands still unprocessed by the GPU. This > actually wouldn't be that hard to organize.
The Savage driver does this. Currently it waits for engine idle before uploading a texture. I thought there must be some more efficient (age-based) method. I havn't looked into the details yet. Do you have a hint that would get me started in the right direction? > > Also, note that there is quite a bit of copying going on: > > - Application calls glTexImage > - Mesa allocates system memory and copies image > - Driver allocates agp buffers and copies image into them > - Card receives blit command and copies image to final destination. > > > Currently Mesa needs to keep the system memory copy because texture > images in card or agp memory can be clobbered by other apps at any time > - Ian's texture manager will address this. > > In the via and sis drivers, texture allocations are permanent, so I've > been able to try a different strategy: > > - Application calls glTexImage > - Mesa allocates AGP/card memory and copies texture directly to final > destination (using memcpy().) > > This resulted in an approximate 2x speedup in texture downloads against > a strategy similar to the first one outlined (but implemented with cpu > copies, not a hostdata blit). The Savage driver uploads textures by memcpy (actually a bit more complicated due to texture tiling) to destination memory. I did some optimization of that tiled upload recently. Now oprofile shows that most CPU usage in texdown is not in the tiled upload but in mesa's texstore-functions. I suppose they could use some optimization too. -- | Felix Kühling <[EMAIL PROTECTED]> http://fxk.de.vu | | PGP Fingerprint: 6A3C 9566 5B30 DDED 73C3 B152 151C 5CC1 D888 E595 | ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
