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. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
