[Mesa-dev] [PATCH v2 17/24] anv: Use blorp_ccs_ambiguate instead of fast-clears
Jason Ekstrand
jason at jlekstrand.net
Wed Jan 31 01:14:39 UTC 2018
On Tue, Jan 30, 2018 at 5:03 PM, Nanley Chery <nanleychery at gmail.com> wrote:
> On Tue, Jan 30, 2018 at 04:25:59PM -0800, Jason Ekstrand wrote:
> > On Tue, Jan 30, 2018 at 2:54 PM, Nanley Chery <nanleychery at gmail.com>
> wrote:
> >
> > > On Fri, Jan 19, 2018 at 03:47:34PM -0800, Jason Ekstrand wrote:
> > > > Even though the blorp pass looks a bit on the sketchy side, the end
> > > > result in the Vulkan driver is very nice. Instead of having this
> weird
> > > > case where you do a fast clear and then maybe have to resolve, we
> just
> > > > do the ambiguate and are done with it. The ambiguate does exactly
> what
> > > > we want of setting all the CCS values to 0 which puts it inot the
> > > ^
> > > in
>
> Typo.
>
Yup. Meant into
> > > > pass-through state.
> > > >
> > > > This should also improve performance a bit in certain cases. For
> > > > instance, if we did a transition from UNDEFINED to GENERAL for a
> surface
> > > > that doesn't have CCS enabled all the time, we would end up doing a
> > > > fast-clear and then a full resolve which ends up touching every byte
> in
> > > > the main surface as well as the CCS. With the ambiguate pass, that
> > > > transition only touches the CCS.
> > > > ---
> > > > src/intel/vulkan/anv_blorp.c | 5 ++++
> > > > src/intel/vulkan/genX_cmd_buffer.c | 54
> +++++++++---------------------
> > > --------
> > > > 2 files changed, 17 insertions(+), 42 deletions(-)
> > > >
> > > > diff --git a/src/intel/vulkan/anv_blorp.c
> b/src/intel/vulkan/anv_blorp.c
> > > > index 05efc6d..3698543 100644
> > > > --- a/src/intel/vulkan/anv_blorp.c
> > > > +++ b/src/intel/vulkan/anv_blorp.c
> > > > @@ -1792,6 +1792,11 @@ anv_image_ccs_op(struct anv_cmd_buffer
> > > *cmd_buffer,
> > > > surf.surf->format,
> isl_to_blorp_fast_clear_op(
> > > ccs_op));
> > > > break;
> > > > case ISL_AUX_OP_AMBIGUATE:
> > > > + for (uint32_t a = 0; a < layer_count; a++) {
> > > > + const uint32_t layer = base_layer + a;
> > > > + blorp_ccs_ambiguate(&batch, &surf, level, layer);
> > > > + }
> > > > + break;
> > > > default:
> > > > unreachable("Unsupported CCS operation");
> > > > }
> > > > diff --git a/src/intel/vulkan/genX_cmd_buffer.c
> > > b/src/intel/vulkan/genX_cmd_buffer.c
> > > > index 77fdadf..9e2eba3 100644
> > > > --- a/src/intel/vulkan/genX_cmd_buffer.c
> > > > +++ b/src/intel/vulkan/genX_cmd_buffer.c
> > > > @@ -486,15 +486,6 @@ init_fast_clear_state_entry(struct
> anv_cmd_buffer
> > > *cmd_buffer,
> > > > uint32_t plane = anv_image_aspect_to_plane(image->aspects,
> aspect);
> > > > enum isl_aux_usage aux_usage = image->planes[plane].aux_usage;
> > > >
> > > > - /* The resolve flag should updated to signify that
> > > fast-clear/compression
> > > > - * data needs to be removed when leaving the undefined layout.
> Such
> > > data
> > > > - * may need to be removed if it would cause accesses to the color
> > > buffer
> > > > - * to return incorrect data. The fast clear data in CCS_D buffers
> > > should
> > > > - * be removed because CCS_D isn't enabled all the time.
> > > > - */
> > > > - genX(set_image_needs_resolve)(cmd_buffer, image, aspect, level,
> > > > - aux_usage == ISL_AUX_USAGE_NONE);
> > > > -
> > > > /* The fast clear value dword(s) will be copied into a surface
> state
> > > object.
> > > > * Ensure that the restrictions of the fields in the dword(s) are
> > > followed.
> > > > *
> > > > @@ -677,10 +668,9 @@ transition_color_buffer(struct anv_cmd_buffer
> > > *cmd_buffer,
> > > > for (unsigned level = base_level; level < last_level_num;
> level++)
> > > > init_fast_clear_state_entry(cmd_buffer, image, aspect,
> level);
> > > >
> > > > - /* Initialize the aux buffers to enable correct rendering.
> This
> > > operation
> > > > - * requires up to two steps: one to rid the aux buffer of data
> > > that may
> > > > - * cause GPU hangs, and another to ensure that writes done
> > > without aux
> > > > - * will be visible to reads done with aux.
> > > > + /* Initialize the aux buffers to enable correct rendering. In
> > > order to
> > > > + * ensure that things such as storage images work correctly,
> aux
> > > buffers
> > > > + * are initialized to the pass-through state.
> > >
> > > Only CCS is initialized to the pass-through state while MCS is
> > > fast-cleared. We may also want to update the comment below since we're
> > > no longer fast-clearing CCS.
> > >
> >
> > Right. I've replaced this entire comment with:
> >
> > /* Initialize the aux buffers to enable correct rendering. In
> order
> > to
> > * ensure that things such as storage images work correctly, aux
> > buffers
> > * need to be initialized to valid data.
> > *
> > * Having an aux buffer with invalid data is a problem for two
> > reasons:
> > *
> > * 1) Having an invalid value in the buffer can confuse the
> hardware.
> > * For instance, with CCS_E on SKL, a two-bit CCS value of 2 is
> > * invalid and leads to the hardware doing strange things. It
> > * doesn't hang as far as we can tell but rendering corruption
> can
> > * occur.
> > *
> > * 2) If this transition is into the GENERAL layout and we then
> use
> > the
> > * image as a storage image, then we must have the aux buffer
> in
> > the
> > * pass-through state so that, if we then go to texture from
> the
> > * image, we get the results of our storage image writes and
> not
> > the
> > * fast clear color or other random data.
>
> This reads better. Is 2) an actual issue? When we create surface states
> for storage images, we set the aux_usage to NONE.
>
Yes. If you do UNDEFINED -> GENERAL -> use for storage -> RENDER_OPTIMAL +
LOAD_OP_LOAD -> draw to part of it -> TEXTURE_OPTIMAL.
> - Nanley
>
> > *
> > * For CCS both of the problems above are real demonstrable issues.
> > In
> > * that case, the only thing we can do is to perform an ambiguate
> to
> > * transition the aux surface into the pass-through state.
> > *
> > * For MCS, (2) is never an issue because we don't support
> > multisampled
> > * storage images. In theory, issue (1) is a problem with MCS but
> > we've
> > * never seen it in the wild. For 4x and 16x, all bit patters
> could,
> > in
> > * theory, be interpreted as something but we don't know that all
> bit
> > * patterns are actually valid. For 2x and 8x, you could easily
> end
> > up
> > * with the MCS referring to an invalid plane because not all bits
> of
> > * the MCS value are actually used. Even though we've never seen
> > issues
> > * in the wild, it's best to play it safe and initialize the MCS.
> We
> > * can use a fast-clear for MCS because we only ever touch from
> render
> > * and texture (no image load store).
> > */
> >
> > > *
> > > > * Having an aux buffer with invalid data is possible for CCS
> > > buffers
> > > > * SKL+ and for MCS buffers with certain sample counts (2x and
> > > 8x). One
> > > > @@ -692,16 +682,18 @@ transition_color_buffer(struct anv_cmd_buffer
> > > *cmd_buffer,
> > > > * We don't have any data to show that this is a problem, but
> we
> > > want to
> > > > * avoid causing difficult-to-debug problems.
> > > > */
> > > > - if (GEN_GEN >= 9 && image->samples == 1) {
> > > > + if (image->samples == 1) {
> > > > for (uint32_t l = 0; l < level_count; l++) {
> > > > const uint32_t level = base_level + l;
> > > > const uint32_t level_layer_count =
> > > > MIN2(layer_count, anv_image_aux_layers(image, aspect,
> > > level));
> > > > anv_image_ccs_op(cmd_buffer, image, aspect, level,
> > > > base_layer, level_layer_count,
> > > > - ISL_AUX_OP_FAST_CLEAR, false);
> > > > + ISL_AUX_OP_AMBIGUATE, false);
> > > > + genX(set_image_needs_resolve)(cmd_buffer, image,
> > > > + aspect, level, false);
> > > > }
> > > > - } else if (image->samples > 1) {
> > > > + } else {
> > > > if (image->samples == 4 || image->samples == 16) {
> > > > anv_perf_warn(cmd_buffer->device->instance, image,
> > > > "Doing a potentially unnecessary
> fast-clear
> > > to "
> > > > @@ -712,32 +704,10 @@ transition_color_buffer(struct anv_cmd_buffer
> > > *cmd_buffer,
> > > > anv_image_mcs_op(cmd_buffer, image, aspect,
> > > > base_layer, layer_count,
> > > > ISL_AUX_OP_FAST_CLEAR, false);
> > > > - }
> > > > - /* At this point, some elements of the CCS buffer may have the
> > > fast-clear
> > > > - * bit-arrangement. As the user writes to a subresource, we
> need
> > > to have
> > > > - * the associated CCS elements enter the ambiguated state.
> This
> > > enables
> > > > - * reads (implicit or explicit) to reflect the user-written
> data
> > > instead
> > > > - * of the clear color. The only time such elements will not
> > > change their
> > > > - * state as described above, is in a final layout that doesn't
> > > have CCS
> > > > - * enabled. In this case, we must force the associated CCS
> > > buffers of the
> > > > - * specified range to enter the ambiguated state in advance.
> > > > - */
> > > > - if (image->samples == 1 &&
> > > > - image->planes[plane].aux_usage != ISL_AUX_USAGE_CCS_E &&
> > > > - final_layout != VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL)
> {
> > > > - /* The CCS_D buffer may not be enabled in the final layout.
> > > Call this
> > > > - * function again with a initial layout of
> > > COLOR_ATTACHMENT_OPTIMAL
> > > > - * to perform a resolve.
> > > > - */
> > > > - anv_perf_warn(cmd_buffer->device->instance, image,
> > > > - "Performing an additional resolve for CCS_D
> > > layout "
> > > > - "transition. Consider always leaving it on
> or "
> > > > - "performing an ambiguation pass.");
> > > > - transition_color_buffer(cmd_buffer, image, aspect,
> > > > - base_level, level_count,
> > > > - base_layer, layer_count,
> > > > - VK_IMAGE_LAYOUT_COLOR_
> > > ATTACHMENT_OPTIMAL,
> > > > - final_layout);
> > >
> > > Nice to be rid of this.
> > >
> >
> > Yup.
> >
> >
> > > > + for (unsigned level = base_level; level < last_level_num;
> > > level++) {
> > > > + genX(set_image_needs_resolve)(cmd_buffer, image,
> > > > + aspect, level, true);
> > > > + }
> > >
> > > Why set needs resolve true here?
> > >
> >
> > There's no particularly good reason. I'll delete it. We never do MCS
> > resolves anyway. When the time comes for me to go hook up MCS
> fast-clears
> > again, we can sort it out then.
>
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