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
  30 #include "gen_l3_config.h"
  31
  32 /**
  33  * The following diagram shows how we partition the URB:
  34  *
  35  *        16kb or 32kb               Rest of the URB space
  36  *   __________-__________   _________________-_________________
  37  *  /                     \ /                                   \
  38  * +-------------------------------------------------------------+
  39  * |  VS/HS/DS/GS/FS Push  |           VS/HS/DS/GS URB           |
  40  * |       Constants       |               Entries               |
  41  * +-------------------------------------------------------------+
  42  *
  43  * Push constants must be stored at the beginning of the URB space,
  44  * while URB entries can be stored anywhere.  We choose to lay them
  45  * out in pipeline order (VS -> HS -> DS -> GS).
  46  */
  47
  48 /**
  49  * Decide how to partition the URB among the various stages.
  50  *
  51  * \param[in] push_constant_bytes - space allocate for push constants.
  52  * \param[in] urb_size_bytes - total size of the URB (from L3 config).
  53  * \param[in] tess_present - are tessellation shaders active?
  54  * \param[in] gs_present - are geometry shaders active?
  55  * \param[in] entry_size - the URB entry size (from the shader compiler)
  56  * \param[out] entries - the number of URB entries for each stage
  57  * \param[out] start - the starting offset for each stage
  58  */
  59 void
  60 gen_get_urb_config(const struct gen_device_info *devinfo,
  61                    unsigned push_constant_bytes, unsigned urb_size_bytes,
  62                    bool tess_present, bool gs_present,
  63                    const unsigned entry_size[4],
  64                    unsigned entries[4], unsigned start[4])
  65 {
  66    const bool active[4] = { true, tess_present, tess_present, gs_present };
  67
  68    /* URB allocations must be done in 8k chunks. */
  69    const unsigned chunk_size_bytes = 8192;
  70
  71    const unsigned push_constant_chunks =
  72       push_constant_bytes / chunk_size_bytes;
  73    const unsigned urb_chunks = urb_size_bytes / chunk_size_bytes;
  74
  75    /* From p35 of the Ivy Bridge PRM (section 1.7.1: 3DSTATE_URB_GS):
  76     *
  77     *     VS Number of URB Entries must be divisible by 8 if the VS URB Entry
  78     *     Allocation Size is less than 9 512-bit URB entries.
  79     *
  80     * Similar text exists for HS, DS and GS.
  81     */
  82    unsigned granularity[4];
  83    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
  84       granularity[i] = (entry_size[i] < 9) ? 8 : 1;
  85    }
  86
  87    unsigned min_entries[4] = {
  88       /* VS has a lower limit on the number of URB entries.
  89        *
  90        * From the Broadwell PRM, 3DSTATE_URB_VS instruction:
  91        * "When tessellation is enabled, the VS Number of URB Entries must be
  92        *  greater than or equal to 192."
  93        */
  94       [MESA_SHADER_VERTEX] = tess_present && devinfo->gen == 8 ?
  95          192 : devinfo->urb.min_entries[MESA_SHADER_VERTEX],
  96
  97       /* There are two constraints on the minimum amount of URB space we can
  98        * allocate:
  99        *
 100        * (1) We need room for at least 2 URB entries, since we always operate
 101        * the GS in DUAL_OBJECT mode.
 102        *
 103        * (2) We can't allocate less than nr_gs_entries_granularity.
 104        */
 105       [MESA_SHADER_GEOMETRY] = gs_present ? 2 : 0,
 106
 107       [MESA_SHADER_TESS_CTRL] = tess_present ? 1 : 0,
 108
 109       [MESA_SHADER_TESS_EVAL] = tess_present ?
 110          devinfo->urb.min_entries[MESA_SHADER_TESS_EVAL] : 0,
 111    };
 112
 113    /* Min VS Entries isn't a multiple of 8 on Cherryview/Broxton; round up.
 114     * Round them all up.
 115     */
 116    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 117       min_entries[i] = ALIGN(min_entries[i], granularity[i]);
 118    }
 119
 120    unsigned entry_size_bytes[4];
 121    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 122       entry_size_bytes[i] = 64 * entry_size[i];
 123    }
 124
 125    /* Initially, assign each stage the minimum amount of URB space it needs,
 126     * and make a note of how much additional space it "wants" (the amount of
 127     * additional space it could actually make use of).
 128     */
 129    unsigned chunks[4];
 130    unsigned wants[4];
 131    unsigned total_needs = push_constant_chunks;
 132    unsigned total_wants = 0;
 133
 134    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 135       if (active[i]) {
 136          chunks[i] = DIV_ROUND_UP(min_entries[i] * entry_size_bytes[i],
 137                                   chunk_size_bytes);
 138
 139          wants[i] =
 140             DIV_ROUND_UP(devinfo->urb.max_entries[i] * entry_size_bytes[i],
 141                          chunk_size_bytes) - chunks[i];
 142       } else {
 143          chunks[i] = 0;
 144          wants[i] = 0;
 145       }
 146
 147       total_needs += chunks[i];
 148       total_wants += wants[i];
 149    }
 150
 151    assert(total_needs <= urb_chunks);
 152
 153    /* Mete out remaining space (if any) in proportion to "wants". */
 154    unsigned remaining_space = MIN2(urb_chunks - total_needs, total_wants);
 155
 156    if (remaining_space > 0) {
 157       for (int i = MESA_SHADER_VERTEX;
 158            total_wants > 0 && i <= MESA_SHADER_TESS_EVAL; i++) {
 159          unsigned additional = (unsigned)
 160             roundf(wants[i] * (((float) remaining_space) / total_wants));
 161          chunks[i] += additional;
 162          remaining_space -= additional;
 163          total_wants -= wants[i];
 164       }
 165
 166       chunks[MESA_SHADER_GEOMETRY] += remaining_space;
 167    }
 168
 169    /* Sanity check that we haven't over-allocated. */
 170    unsigned total_chunks = push_constant_chunks;
 171    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 172       total_chunks += chunks[i];
 173    }
 174    assert(total_chunks <= urb_chunks);
 175
 176    /* Finally, compute the number of entries that can fit in the space
 177     * allocated to each stage.
 178     */
 179    for (int i = MESA_SHADER_VERTEX; i <= MESA_SHADER_GEOMETRY; i++) {
 180       entries[i] = chunks[i] * chunk_size_bytes / entry_size_bytes[i];
 181
 182       /* Since we rounded up when computing wants[], this may be slightly
 183        * more than the maximum allowed amount, so correct for that.
 184        */
 185       entries[i] = MIN2(entries[i], devinfo->urb.max_entries[i]);
 186
 187       /* Ensure that we program a multiple of the granularity. */
 188       entries[i] = ROUND_DOWN_TO(entries[i], granularity[i]);
 189
 190       /* Finally, sanity check to make sure we have at least the minimum
 191        * number of entries needed for each stage.
 192        */
 193       assert(entries[i] >= min_entries[i]);
 194    }
 195
 196    /* Lay out the URB in pipeline order: push constants, VS, HS, DS, GS. */
 197    start[0] = push_constant_chunks;
 198    for (int i = MESA_SHADER_TESS_CTRL; i <= MESA_SHADER_GEOMETRY; i++) {
 199       start[i] = start[i - 1] + chunks[i - 1];
 200    }
 201 }