On Tue, Jan 28, 2014 at 01:15:35PM +0200, Ville Syrjälä wrote: > On Mon, Jan 27, 2014 at 10:43:07PM +0000, Chris Wilson wrote: > > As the VM do not track activity of objects and instead use a large > > hammer to forcibly idle and evict all of their associated objects when > > one is released, it is possible for that to cause a recursion when we > > need to wait for free space on a ring and call retire requests. > > (intel_ring_begin -> intel_ring_wait_request -> > > i915_gem_retire_requests_ring -> i915_gem_context_free -> > > i915_gem_evict_vm -> i915_gpu_idle -> intel_ring_begin etc) > > > > In order to remove the requirement for calling retire-requests from > > intel_ring_wait_request, we have to inline a couple of steps from > > retiring requests, notably we have to record the position of the request > > we wait for and use that to update the available ring space. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Looks good to me. > Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > I do have a couple of questions about request->tail though. > > We set it to -1 in intel_ring_wait_request(). Isn't that going to cause > problems for i915_request_guilty()? > > When not -1, request->tail points to just before the commands that > .add_request() adds to the ring. So that means intel_ring_wait_request() > might have to wait for one extra request, and I guess more importantly > if the GPU hangs inside the .add_request() commands, we won't attribute > the hang to the request in question. Was it designe to be that way, or > is there a bug here? Ah good questions. I completely forgot about the behaviour here when we adjusted this for hangstats... Setting it to -1 should not confuse the guilty search since that should be done (or at least changed so that is) based on a completion search. After making that change, we should be able to set request->tail back to being just after the request. Also I think we are quite safe to drop the manipulation of request->tail inside intel_ring_wait_request(). -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
