<ogerlitz@xxxxxxxxxxxx>,Sagi Grimberg <sagig@xxxxxxxxxxxx>,Shachar Raindel <raindel@xxxxxxxxxxxx>,Liran Liss <liranl@xxxxxxxxxxxx>,Roland Dreier <roland@xxxxxxxxxxxxxxx>,"Sander, Ben" <ben.sander@xxxxxxx>,"Stoner, Greg" <Greg.Stoner@xxxxxxx>,"Bridgman, John" <John.Bridgman@xxxxxxx>,"Mantor, Michael" <Michael.Mantor@xxxxxxx>,"Blinzer, Paul" <Paul.Blinzer@xxxxxxx>,"Morichetti, Laurent" <Laurent.Morichetti@xxxxxxx>,"Deucher, Alexander" <Alexander.Deucher@xxxxxxx>,"Gabbay, Oded" <Oded.Gabbay@xxxxxxx>,Davidlohr Bueso <davidlohr@xxxxxx> Message-ID: <0bf54468-3ed1-4cd4-b771-4836c78dde14@xxxxxxxxxxxxxxxxx> Nothing wrong with device-side memory, but not having it accessible by the CPU seems fundamentally brown from the point of view of unified memory addressing. On May 6, 2014 9:54:08 AM PDT, Jerome Glisse <j.glisse@xxxxxxxxx> wrote: >On Tue, May 06, 2014 at 12:47:16PM -0400, Rik van Riel wrote: >> On 05/06/2014 12:34 PM, Linus Torvalds wrote: >> > On Tue, May 6, 2014 at 9:30 AM, Rik van Riel <riel@xxxxxxxxxx> >wrote: >> >> >> >> The GPU runs a lot faster when using video memory, instead >> >> of system memory, on the other side of the PCIe bus. >> > >> > The nineties called, and they want their old broken model back. >> > >> > Get with the times. No high-performance future GPU will ever run >> > behind the PCIe bus. We still have a few straggling historical >> > artifacts, but everybody knows where the future is headed. >> > >> > They are already cache-coherent because flushing caches etc was too >> > damn expensive. They're getting more so. >> >> I suppose that VRAM could simply be turned into a very high >> capacity CPU cache for the GPU, for the case where people >> want/need an add-on card. >> >> With a few hundred MB of "CPU cache" on the video card, we >> could offload processing to the GPU very easily, without >> having to worry about multiple address or page table formats >> on the CPU side. >> >> A new generation of GPU hardware seems to come out every >> six months or so, so I guess we could live with TLB >> invalidations to the first generations of hardware being >> comically slow :) >> > >I do not want to speak for any GPU manufacturer but i think it is safe >to say that there will be dedicated memory for GPU for a long time. It >is not going anywhere soon and it is a lot more than few hundred MB, >think several GB. If you think about 4k, 8k screen you really gonna >want >8GB at least on desktop computer and for compute you will likely see >16GB or 32GB as common size. > >Again i stress that there is nothing on the horizon that let me believe >that regular memory associated to CPU will ever come close to the >bandwith >that exist with memory associated to GPU. It is already more than 10 >times >faster on GPU and as far as i know the gap will grow even more in the >next >generation. > >So dedicated memory to gpu should not be discarded as something that is >vanishing quite the contrary it should be acknowledge as something that >is >here to stay a lot longer afaict. > >Cheers, >Jérôme -- Sent from my mobile phone. Please pardon brevity and lack of formatting. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>