On Thu, Jan 22, 2015 at 01:41:48PM +0000, Tvrtko Ursulin wrote:
>
> On 01/22/2015 11:42 AM, Chris Wilson wrote:
> >>+ if (args->flags & I915_EXEC_FENCE_OUT) {
> >>+ ret = i915_create_sync_fence_ring(ring, ctx,
> >>+ &sync_fence, &fence_fd);
> >>+ if (ret)
> >>+ goto sync_err;
> >>+ }
> >>+
> >> ret = dev_priv->gt.do_execbuf(dev, file, ring, ctx, args,
> >> &eb->vmas, batch_obj, exec_start, flags);
> >
> >You emit the fence prior to the execution of the batch? Interesting. Not
> >exactly where I would expect the fence. Both before/after are
> >justifiable.
>
> What do yo consider emitting? To me that is fd_install and that
> happens after request was successfully submitted. I thought it is
> tidier to set up required objects before and then install the fence,
> or discard it, depending on the outcome. You think differently?
i915_create_sync_fence_ring() inserts a breadcrumb into the ring that
fires before we execute the execbuf (which then gets its own request +
breadcrumb).
I believe the intention is to hook the fence into the breadcrumb that
fires after the execbuf, i.e. to add it to the execbuf request rather
than create a new request all for itself.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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