2012/2/1 Michel Dänzer <michel@xxxxxxxxxxx>: > On Die, 2012-01-31 at 22:08 +0100, Marek Olšák wrote: >> 2012/1/31 Jerome Glisse <j.glisse@xxxxxxxxx>: >> > On Tue, Jan 31, 2012 at 06:56:01PM +0100, Michel Dänzer wrote: >> >> On Die, 2012-01-31 at 16:59 +0000, Simon Farnsworth wrote: >> >> > Userspace currently busywaits for fences to complete; on my workload, this >> >> > busywait consumes 10% of the available CPU time. >> >> > >> >> > Provide an ioctl so that userspace can wait for an EOP interrupt that >> >> > corresponds to a previous EVENT_WRITE_EOP. >> >> > >> >> > Signed-off-by: Simon Farnsworth <simon.farnsworth@xxxxxxxxxxxx> >> >> > --- >> >> > I've been working on top of Jerome's tiling patches, so this doesn't apply >> >> > directly on top of current upstream kernels. I can easily rebase to another >> >> > version upon request - just point me to a git tree. >> >> > >> >> > My goal is to remove the sched_yield in Mesa's r600_fence_finish given up to >> >> > date enough kernel; I hope, though, that the interface is clean enough for >> >> > other users to extend it in the future (e.g. using compute rings). >> >> >> >> I'm afraid not: Unless I'm missing something, userspace can't know which >> >> ring the kernel submitted the CS to, and the kernel can't guess which >> >> ring userspace needs to wait for. >> > >> > iirc the plan was to add a return value to cs ioctl and add an ioctl to >> > allow to wait on this return value. ie allowing userspace to wait on >> > specific submited cs. >> >> You don't need a new API for that, r300g already does that. It adds a >> dummy relocation and later uses GEM_WAIT_IDLE to wait for it. r600g >> can be updated to do the same thing without kernel changes (besides, >> we must support the old kernels as well, so this is a no-brainer). > > One minor problem being that this doesn't support a timeout without > spinning. Shouldn't be relevant for Simon's problem though. > > >> What would be much more useful is to be able to wait for a fence, >> which can be in the middle of a CS. Now that's something that would >> justify changes in the kernel interface. > > To take advantage of that, one would also need to change Gallium such > that it's possible to get a fence without a flush. There is PIPE_QUERY_GPU_FINISHED, which should be used for that purpose. We already agreed in another discussion that this is the way fences should be done in Gallium. It's just a matter of updating st/mesa to use it. Marek _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
