[Mesa-dev] [v2 4/9] i965: Estimate batch space per shader stage

[Topi Pohjolainen]

Current estimate doesn't consider space needed for surface states
and it only calculates for one shader stage. Each stage can have
its own sampler and surface state configuration.

While this is only matter of runtime dynamics we don't seem to hit
it currently. However, this becomes visible with blorp tex uploads
(HSW with piglit test max-samplers). One runs out of space while
batch wrapping isn't allowed.

v2: Rebase on top of current upstream
v3: Take binding table alignment into account (Jason)

Signed-off-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
CC: Kenneth Graunke <kenneth at whitecape.org>
CC: Jason Ekstrand <jason at jlekstrand.net>
---
 src/mesa/drivers/dri/i965/brw_draw.c | 53 ++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index 6ca6a7a..dba8603 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -395,6 +395,55 @@ brw_postdraw_set_buffers_need_resolve(struct brw_context *brw)
    }
 }
 
+static unsigned
+brw_get_num_active_samplers(const struct gl_context *ctx,
+                            const struct gl_program *prog)
+{
+   const unsigned last = util_last_bit(prog->SamplersUsed);
+   unsigned count = 0;
+
+   for (unsigned s = 0; s < last; s++) {
+      if (prog->SamplersUsed & (1 << s)) {
+         const unsigned unit = prog->SamplerUnits[s];
+         if (ctx->Texture.Unit[unit]._Current)
+            ++count;
+      }
+   }
+
+   return count;
+}
+
+static unsigned
+brw_estimate_batch_space_for_textures(const struct brw_context *brw)
+{
+   const struct gl_context *ctx = &brw->ctx;
+   unsigned total = 0;
+
+   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
+      const struct gl_program *prog = ctx->_Shader->CurrentProgram[i];
+
+      if (prog == NULL)
+         continue;
+
+      const unsigned num_samplers = brw_get_num_active_samplers(ctx, prog);
+      const unsigned sampler_needs_per_tex_unit =
+         16 /* sampler_state_size */ +
+         sizeof(struct gen5_sampler_default_color);
+      const unsigned surface_state_needs_per_tex_unit =
+         ALIGN(brw->isl_dev.ss.size, brw->isl_dev.ss.align);
+      const unsigned total_per_tex_unit = sampler_needs_per_tex_unit +
+                                          surface_state_needs_per_tex_unit;
+      total += (num_samplers * total_per_tex_unit);
+
+      /* Also consider space and alignment needed for binding table pointers,
+       * each taking four bytes.
+       */
+      total += ALIGN(num_samplers * 4, 64);
+   }
+
+   return total;
+}
+
 /* May fail if out of video memory for texture or vbo upload, or on
  * fallback conditions.
  */
@@ -466,11 +515,9 @@ brw_try_draw_prims(struct gl_context *ctx,
 
    for (i = 0; i < nr_prims; i++) {
       int estimated_max_prim_size;
-      const int sampler_state_size = 16;
 
       estimated_max_prim_size = 512; /* batchbuffer commands */
-      estimated_max_prim_size += BRW_MAX_TEX_UNIT *
-         (sampler_state_size + sizeof(struct gen5_sampler_default_color));
+      estimated_max_prim_size += brw_estimate_batch_space_for_textures(brw);
       estimated_max_prim_size += 1024; /* gen6 VS push constants */
       estimated_max_prim_size += 1024; /* gen6 WM push constants */
       estimated_max_prim_size += 512; /* misc. pad */
-- 
2.9.3