On Wed, Mar 30, 2011 at 10:07 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > On Wed, 30 Mar 2011 09:28:07 -0400, Jerome Glisse <j.glisse@xxxxxxxxx> wrote: >> On Wed, Mar 30, 2011 at 3:32 AM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: >> > On Wed, 30 Mar 2011 07:57:49 +1000, Dave Airlie <airlied@xxxxxxxxx> wrote: >> >> On Wed, Mar 30, 2011 at 7:04 AM, Jerome Glisse <j.glisse@xxxxxxxxx> wrote: >> >> > What i had in mind was something little bit more advance that pwrite, >> >> > somethings that would take width,height,pitch of userpage and would be >> >> > able to perform proper blit. But yes pwrite in intel is kind of >> >> > limited. >> >> >> >> TTM has support for userpage binding we just don't use it. >> > >> > Yes, and I've been experimenting with the same in GEM to great effect in >> > the DDX. The complication remains in managing the CPU synchronisation, >> > which suggests that it would only be useful for STREAM_DRAW objects (and >> > perhaps the sub-region updates to STATIC_DRAW). (And for readback, if >> > retrieving the data were the actual bottleneck.) >> >> What do you mean by CPU synchronisation ? In what i had in mind the >> upload/download would block userspace until operation is, this would >> make upload/dowload barrier of course it doesn't play well with >> usecase where you keep uploading/downloading (idea to aleviate that is >> to allow several download/upload in one ioctl call). > > Yes, that is the issue: having to control access to the user pages whilst > they are in use by the GPU. A completely synchronous API for performing > a single pwrite with the blitter is too slow, much slower than doing an > uncached write with the CPU and queueing up multiple blits (as we > currently do). > > The API I ended up with for the pwrite using the BLT was to specify a 2D > region (addr, width, height, stride, flags etc) and list of clip rects. At > which point I grew disenchanted, and realised that simply creating a bo > for mapping user pages was the far better solution. > -Chris > > -- > Chris Wilson, Intel Open Source Technology Centre > What kind of usage didn't played well with synchronous upload/download ? X, GL ? Cheers, Jerome _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
