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radeonsi: improve comments in si_emit_derived_tess_state

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Reviewed-by: Zoltán Böszörményi <zboszor@gmail.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9028>
This commit is contained in:
Marek Olšák
2021-02-09 18:58:54 -05:00
parent 98ea523e00
commit 9db4b331f9
1 changed files with 8 additions and 11 deletions
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src/gallium/drivers/radeonsi/si_state_draw.cpp
+8 -11
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@@ -264,9 +264,10 @@ static void si_emit_derived_tess_state(struct si_context *sctx,
lds_per_patch = MAX2(input_patch_size, output_patch_size);
}
/* Ensure that we only need one wave per SIMD so we don't need to check
* resource usage. Also ensures that the number of tcs in and out
* vertices per threadgroup are at most 256.
/* Ensure that we only need 4 waves per CU, so that we don't need to check
* resource usage (such as whether we have enough VGPRs to fit the whole
* threadgroup into the CU). It also ensures that the number of tcs in and out
* vertices per threadgroup are at most 256, which is the hw limit.
*/
unsigned max_verts_per_patch = MAX2(num_tcs_input_cp, num_tcs_output_cp);
*num_patches = 256 / max_verts_per_patch;
@@ -290,11 +291,8 @@ static void si_emit_derived_tess_state(struct si_context *sctx,
/* Make sure that the data fits in LDS. This assumes the shaders only
* use LDS for the inputs and outputs.
*
* While GFX7 can use 64K per threadgroup, there is a hang on Stoney
* with 2 CUs if we use more than 32K. The closed Vulkan driver also
* uses 32K at most on all GCN chips.
*
* Use 16K so that we can fit 2 workgroups on the same CU.
* The maximum allowed LDS size is 32K. Higher numbers can hang.
* Use 16K as the maximum, so that we can fit 2 workgroups on the same CU.
*/
ASSERTED unsigned max_lds_size = 32 * 1024; /* hw limit */
unsigned target_lds_size = 16 * 1024; /* target at least 2 workgroups per CU, 16K each */
@@ -302,9 +300,8 @@ static void si_emit_derived_tess_state(struct si_context *sctx,
*num_patches = MAX2(*num_patches, 1);
assert(*num_patches * lds_per_patch <= max_lds_size);
/* Make sure that vector lanes are reasonably occupied. It probably
* doesn't matter much because this is LS-HS, and TES is likely to
* occupy significantly more CUs.
/* Make sure that vector lanes are fully occupied by cutting off the last wave
* if it's only partially filled.
*/
unsigned temp_verts_per_tg = *num_patches * max_verts_per_patch;
unsigned wave_size = sctx->screen->ge_wave_size;