On Tue, Jun 22, 2021 at 9:37 AM Christian König <ckoenig.leichtzumerken@xxxxxxxxx> wrote: > > Am 22.06.21 um 01:29 schrieb Jason Gunthorpe: > > On Mon, Jun 21, 2021 at 10:24:16PM +0300, Oded Gabbay wrote: > > > >> Another thing I want to emphasize is that we are doing p2p only > >> through the export/import of the FD. We do *not* allow the user to > >> mmap the dma-buf as we do not support direct IO. So there is no access > >> to these pages through the userspace. > > Arguably mmaping the memory is a better choice, and is the direction > > that Logan's series goes in. Here the use of DMABUF was specifically > > designed to allow hitless revokation of the memory, which this isn't > > even using. > > The major problem with this approach is that DMA-buf is also used for > memory which isn't CPU accessible. > > That was one of the reasons we didn't even considered using the mapping > memory approach for GPUs. > > Regards, > Christian. > > > > > So you are taking the hit of very limited hardware support and reduced > > performance just to squeeze into DMABUF.. Thanks Jason for the clarification, but I honestly prefer to use DMA-BUF at the moment. It gives us just what we need (even more than what we need as you pointed out), it is *already* integrated and tested in the RDMA subsystem, and I'm feeling comfortable using it as I'm somewhat familiar with it from my AMD days. I'll go and read Logan's patch-set to see if that will work for us in the future. Please remember, as Daniel said, we don't have struct page backing our device memory, so if that is a requirement to connect to Logan's work, then I don't think we will want to do it at this point. Thanks, Oded > > > > Jason > > _______________________________________________ > > Linaro-mm-sig mailing list > > Linaro-mm-sig@xxxxxxxxxxxxxxxx > > https://lists.linaro.org/mailman/listinfo/linaro-mm-sig >
