src/intel/common/gen_urb_config.c

   1 /*
   2  * Copyright (c) 2011 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include <stdlib.h>
  25 #include <math.h>
  26
  27 #include "util/macros.h"
  28 #include "main/macros.h"
  29 #include "compiler/shader_enums.h"
  30
  31 #include "gen_l3_config.h"
  32
  33 /**
  34  * The following diagram shows how we partition the URB:
  35  *
  36  *        16kb or 32kb               Rest of the URB space
  37  *   __________-__________   _________________-_________________
  38  *  /                     \ /                                   \
  39  * +-------------------------------------------------------------+
  40  * |  VS/HS/DS/GS/FS Push  |           VS/HS/DS/GS URB           |
  41  * |       Constants       |               Entries               |
  42  * +-------------------------------------------------------------+
  43  *
  44  * Push constants must be stored at the beginning of the URB space,
  45  * while URB entries can be stored anywhere.  We choose to lay them
  46  * out in pipeline order (VS -> HS -> DS -> GS).
  47  */
  48
  49 /**
  50  * Decide how to partition the URB among the various stages.
  51  *
  52  * \param[in] push_constant_bytes - space allocate for push constants.
  53  * \param[in] urb_size_bytes - total size of the URB (from L3 config).
  54  * \param[in] tess_present - are tessellation shaders active?
  55  * \param[in] gs_present - are geometry shaders active?
  56  * \param[in] entry_size - the URB entry size (from the shader compiler)
  57  * \param[out] entries - the number of URB entries for each stage
  58  * \param[out] start - the starting offset for each stage
  59  */
  60 void
  61 gen_get_urb_config(const struct gen_device_info *devinfo,
  62                    unsigned push_constant_bytes, unsigned urb_size_bytes,
  63                    bool tess_present, bool gs_present,
  64                    const unsigned entry_size[4],
  65                    unsigned entries[4], unsigned start[4])
  66 {
  67    const bool active[4] = { true, tess_present, tess_present, gs_present };
  68
  69    /* URB allocations must be done in 8k chunks. */
  70    const unsigned chunk_size_bytes = 8192;
  71
  72    const unsigned push_constant_chunks =
  73       push_constant_bytes / chunk_size_bytes;
  74    const unsigned urb_chunks = urb_size_bytes / chunk_size_bytes;
  75
  76    /* From p35 of the Ivy Bridge PRM (section 1.7.1: 3DSTATE_URB_GS):
  77     *
  78     *     VS Number of URB Entries must be divisible by 8 if the VS URB Entry
  79     *     Allocation Size is less than 9 512-bit URB entries.
  80     *
  81     * Similar text exists for HS, DS and GS.
  82     */
  83    unsigned granularity[4];
  84    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
  85       granularity[i] = (entry_size[i] < 9) ? 8 : 1;
  86    }
  87
  88    unsigned min_entries[4] = {
  89       /* VS has a lower limit on the number of URB entries.
  90        *
  91        * From the Broadwell PRM, 3DSTATE_URB_VS instruction:
  92        * "When tessellation is enabled, the VS Number of URB Entries must be
  93        *  greater than or equal to 192."
  94        */
  95       [MESA_SHADER_VERTEX] = tess_present && devinfo->gen == 8 ?
  96          192 : devinfo->urb.min_entries[MESA_SHADER_VERTEX],
  97
  98       /* There are two constraints on the minimum amount of URB space we can
  99        * allocate:
 100        *
 101        * (1) We need room for at least 2 URB entries, since we always operate
 102        * the GS in DUAL_OBJECT mode.
 103        *
 104        * (2) We can't allocate less than nr_gs_entries_granularity.
 105        */
 106       [MESA_SHADER_GEOMETRY] = gs_present ? 2 : 0,
 107
 108       [MESA_SHADER_TESS_CTRL] = tess_present ? 1 : 0,
 109
 110       [MESA_SHADER_TESS_EVAL] = tess_present ?
 111          devinfo->urb.min_entries[MESA_SHADER_TESS_EVAL] : 0,
 112    };
 113
 114    /* Min VS Entries isn't a multiple of 8 on Cherryview/Broxton; round up.
 115     * Round them all up.
 116     */
 117    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 118       min_entries[i] = ALIGN(min_entries[i], granularity[i]);
 119    }
 120
 121    unsigned entry_size_bytes[4];
 122    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 123       entry_size_bytes[i] = 64 * entry_size[i];
 124    }
 125
 126    /* Initially, assign each stage the minimum amount of URB space it needs,
 127     * and make a note of how much additional space it "wants" (the amount of
 128     * additional space it could actually make use of).
 129     */
 130    unsigned chunks[4];
 131    unsigned wants[4];
 132    unsigned total_needs = push_constant_chunks;
 133    unsigned total_wants = 0;
 134
 135    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 136       if (active[i]) {
 137          chunks[i] = DIV_ROUND_UP(min_entries[i] * entry_size_bytes[i],
 138                                   chunk_size_bytes);
 139
 140          wants[i] =
 141             DIV_ROUND_UP(devinfo->urb.max_entries[i] * entry_size_bytes[i],
 142                          chunk_size_bytes) - chunks[i];
 143       } else {
 144          chunks[i] = 0;
 145          wants[i] = 0;
 146       }
 147
 148       total_needs += chunks[i];
 149       total_wants += wants[i];
 150    }
 151
 152    assert(total_needs <= urb_chunks);
 153
 154    /* Mete out remaining space (if any) in proportion to "wants". */
 155    unsigned remaining_space = MIN2(urb_chunks - total_needs, total_wants);
 156
 157    if (remaining_space > 0) {
 158       for (int i = MESA_SHADER_VERTEX;
 159            total_wants > 0 && i <= MESA_SHADER_TESS_EVAL; i++) {
 160          unsigned additional = (unsigned)
 161             roundf(wants[i] * (((float) remaining_space) / total_wants));
 162          chunks[i] += additional;
 163          remaining_space -= additional;
 164          total_wants -= wants[i];
 165       }
 166
 167       chunks[MESA_SHADER_GEOMETRY] += remaining_space;
 168    }
 169
 170    /* Sanity check that we haven't over-allocated. */
 171    unsigned total_chunks = push_constant_chunks;
 172    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 173       total_chunks += chunks[i];
 174    }
 175    assert(total_chunks <= urb_chunks);
 176
 177    /* Finally, compute the number of entries that can fit in the space
 178     * allocated to each stage.
 179     */
 180    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 181       entries[i] = chunks[i] * chunk_size_bytes / entry_size_bytes[i];
 182
 183       /* Since we rounded up when computing wants[], this may be slightly
 184        * more than the maximum allowed amount, so correct for that.
 185        */
 186       entries[i] = MIN2(entries[i], devinfo->urb.max_entries[i]);
 187
 188       /* Ensure that we program a multiple of the granularity. */
 189       entries[i] = ROUND_DOWN_TO(entries[i], granularity[i]);
 190
 191       /* Finally, sanity check to make sure we have at least the minimum
 192        * number of entries needed for each stage.
 193        */
 194       assert(entries[i] >= min_entries[i]);
 195    }
 196
 197    /* Lay out the URB in pipeline order: push constants, VS, HS, DS, GS. */
 198    int next = push_constant_chunks;
 199    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 200       if (entries[i]) {
 201          start[i] = next;
 202          next += chunks[i];
 203       } else {
 204          /* Just put disabled stages at the beginning. */
 205          start[i] = 0;
 206       }
 207    }
 208 }