Thomas Hellström wrote: > Benjamin Herrenschmidt wrote: >> On Tue, 2006-09-19 at 11:27 +0200, Thomas Hellström wrote: >> >> >>> But this should be the same problem encountered by the agpgart driver? >>> x86 and x86-64 calls change_page_attr() to take care of this. >>> On powerpc it is simply a noop. (<asm/agp.h>) >>> >> >> Possibly. We sort-of ignore the issue for now on PowerPC and happen to >> be lucky most of the time because 32 bits PowerPC aren't that agressive >> at prefetching... >> >> I haven't looked at change_page_attr() implementation on x86 but I know >> they also map the linear mapping with large pages. I don't know what >> happens if you start trying to change a single page attribute. x86 can >> breakup that large page into 4k pages, so maybe that's what happens. >> >> > Yes, I think that's what happens. I know some Athlon chips had a big > issue with this some time ago. > > I notice there are special functions in <agp.h> to alloc / free GATT > pages, so the general idea might be to have a pool of uncached pages > in the future for powerpc? Even better would perhaps be to have pages > that aren't mapped for the kernel. (like highmem pages on x86). > As a side note, it's not always possible to map the whole video memory. For example on ATI chips you can't map VRAM above 128MB, on Nvidia you can't above 256MB. Still, that memory has to be managed somehow. In that case, such memory areas will be hidden from the application anyway.
Stephane ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
