[Mesa-dev] [PATCH v3 02/14] i965/miptree: Allocate HiZ up-front

[Pohjolainen, Topi]

On Mon, Jul 17, 2017 at 03:29:32PM +0300, Pohjolainen, Topi wrote:
> On Fri, Jul 14, 2017 at 03:22:51PM -0700, Chad Versace wrote:
> > On Wed 12 Jul 2017, Jason Ekstrand wrote:
> > > HiZ, like MCS and CCS_E, can compress more than just clear colors so we
> > > want it turned on whenever the miptree is being used as a depth
> > > attachment.  It's theoretically possible for someone to create a depth
> > > texture, upload data with glTexSubImage2D, and texture from it without
> > > ever binding it as a depth target.  If this happens, we would end up
> > > wasting a bit of space by allocating a HiZ surface we never use.
> > > However, this is rather unlikely out side of test cases, so we're better
> > > off just allocating it up-front.
> > > ---
> > 
> > I've read of rendering techniques that use high-quality, pre-rendered
> > cascading shadow maps for scenes with fixed lights. And that would
> > trigger the glTexSubImage2D case. But, even in that case, so little
> > memory is wasted that I don't care.
> > 
> > Reviewed-by: Chad Versace <chadversary at chromium.org>
> 
> I'm now looking at this more after rebasing my isl patches on top. I think
> this shows a bug we have in intel_miptree_choose_aux_usage() - there we
> consider only if format and platform support hiz, but ignore tiling, ending
> up setting HIZ usage even for linear depth.
> 
> Combined with this patch we start to allocate hiz-buffers for linear depth
> buffers used in read_pixels(). Backtrace with my isl support (which should be
> more or less equivalent from this decision making point of you). By chance ISL
> complains unlike i965 (here it actually complains about ISL_SURF_DIM_1D but
> tiling is incompatible as well):
> 
> #4  0x00007ffff1d78e6e in isl_calc_phys_level0_extent_sa (dev=0x7ffff7fa1208, 
>     phys_level0_sa=<synthetic pointer>, msaa_layout=<optimized out>, 
>     tiling=ISL_TILING_HIZ, dim_layout=ISL_DIM_LAYOUT_GEN4_2D, 
>     info=0x7fffffffd6f0) at isl/isl.c:627
> #5  isl_surf_init_s (dev=dev at entry=0x7ffff7fa1208, 
>     surf=surf at entry=0x7fffffffd740, info=info at entry=0x7fffffffd6f0)
>     at isl/isl.c:1474
> #6  0x00007ffff1d78fc9 in isl_surf_get_hiz_surf (dev=dev at entry=0x7ffff7fa1208, 
>     surf=surf at entry=0x555555b024d0, hiz_surf=hiz_surf at entry=0x7fffffffd740)
>     at isl/isl.c:1659
> #7  0x00007ffff1cb4c4a in intel_miptree_alloc_hiz (
>     brw=brw at entry=0x7ffff7f7c040, mt=mt at entry=0x555555b024d0)
>     at intel_mipmap_tree.c:2139
> #8  0x00007ffff1cb8017 in intel_miptree_alloc_aux (
>     brw=brw at entry=0x7ffff7f7c040, mt=0x555555b024d0)
>     at intel_mipmap_tree.c:2178
> #9  0x00007ffff1cb8362 in intel_miptree_create (brw=brw at entry=0x7ffff7f7c040, 
>     target=target at entry=3553, 
>     format=format at entry=MESA_FORMAT_Z24_UNORM_X8_UINT, 
>     first_level=first_level at entry=0, last_level=last_level at entry=0, 
>     width0=<optimized out>, height0=60, depth0=1, num_samples=0, 
>     layout_flags=64) at intel_mipmap_tree.c:971
> #10 0x00007ffff1cb8d14 in intel_miptree_map_blit (slice=0, level=0, 
>     map=0x555555a7c710, mt=0x555555b1b7d0, brw=0x7ffff7f7c040)
>     at intel_mipmap_tree.c:3247
> #11 intel_miptree_map (brw=brw at entry=0x7ffff7f7c040, mt=0x555555b1b7d0, 
>     level=0, slice=0, x=x at entry=60, y=y at entry=100, w=60, h=60, mode=1, 
>     out_ptr=0x7fffffffdaa8, out_stride=0x7fffffffdab0)
>     at intel_mipmap_tree.c:3817
> #12 0x00007ffff1cb252f in intel_map_renderbuffer (ctx=0x7ffff7f7c040, 
>     rb=0x5555558d2f60, x=60, y=100, w=<optimized out>, h=<optimized out>, 
>     mode=1, out_map=0x7fffffffdb98, out_stride=0x7fffffffdb90)
>     at intel_fbo.c:169
> #13 0x00007ffff19eef3b in read_depth_pixels (packing=0x7fffffffdce0, 

This should be sufficient (at least works for the case I was debugging):

diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index ecd57cbf30..5eb778541f 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -219,6 +219,9 @@ intel_miptree_supports_hiz(struct brw_context *brw,
    if (!brw->has_hiz)
       return false;
 
+   if (mt->tiling != I915_TILING_Y)
+      return false;
+
    switch (mt->format) {
    case MESA_FORMAT_Z_FLOAT32:
    case MESA_FORMAT_Z32_FLOAT_S8X24_UINT: