sysdeps/x86/cpu-tunables.c

   1 /* x86 CPU feature tuning.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2017-2018 Free Software Foundation, Inc.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #if HAVE_TUNABLES
  20 # define TUNABLE_NAMESPACE tune
  21 # include <stdbool.h>
  22 # include <stdint.h>
  23 # include <unistd.h>            /* Get STDOUT_FILENO for _dl_printf.  */
  24 # include <elf/dl-tunables.h>
  25 # include <string.h>
  26 # include <cpu-features.h>
  27 # include <ldsodefs.h>
  28
  29 /* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a
  30    since IFUNC must be set up by init_cpu_features.  */
  31 # if defined USE_MULTIARCH && !defined SHARED
  32 #  ifdef __x86_64__
  33 #   define DEFAULT_MEMCMP       __memcmp_sse2
  34 #  else
  35 #   define DEFAULT_MEMCMP       __memcmp_ia32
  36 #  endif
  37 extern __typeof (memcmp) DEFAULT_MEMCMP;
  38 # else
  39 #  define DEFAULT_MEMCMP        memcmp
  40 # endif
  41
  42 # define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len)          \
  43   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  44   if (!DEFAULT_MEMCMP (f, #name, len))                                  \
  45     {                                                                   \
  46       cpu_features->cpuid[index_cpu_##name].reg_##name                  \
  47         &= ~bit_cpu_##name;                                             \
  48       break;                                                            \
  49     }
  50
  51 /* Disable an ARCH feature NAME.  We don't enable an ARCH feature which
  52    isn't available.  */
  53 # define CHECK_GLIBC_IFUNC_ARCH_OFF(f, cpu_features, name, len)         \
  54   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  55   if (!DEFAULT_MEMCMP (f, #name, len))                                  \
  56     {                                                                   \
  57       cpu_features->feature[index_arch_##name]                          \
  58         &= ~bit_arch_##name;                                            \
  59       break;                                                            \
  60     }
  61
  62 /* Enable/disable an ARCH feature NAME.  */
  63 # define CHECK_GLIBC_IFUNC_ARCH_BOTH(f, cpu_features, name, disable,    \
  64                                     len)                                \
  65   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  66   if (!DEFAULT_MEMCMP (f, #name, len))                                  \
  67     {                                                                   \
  68       if (disable)                                                      \
  69         cpu_features->feature[index_arch_##name]                        \
  70           &= ~bit_arch_##name;                                          \
  71       else                                                              \
  72         cpu_features->feature[index_arch_##name]                        \
  73           |= bit_arch_##name;                                           \
  74       break;                                                            \
  75     }
  76
  77 /* Enable/disable an ARCH feature NAME.  Enable an ARCH feature only
  78    if the ARCH feature NEED is also enabled.  */
  79 # define CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH(f, cpu_features, name,   \
  80                                                need, disable, len)      \
  81   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  82   if (!DEFAULT_MEMCMP (f, #name, len))                                  \
  83     {                                                                   \
  84       if (disable)                                                      \
  85         cpu_features->feature[index_arch_##name]                        \
  86           &= ~bit_arch_##name;                                          \
  87       else if (CPU_FEATURES_ARCH_P (cpu_features, need))                \
  88         cpu_features->feature[index_arch_##name]                        \
  89           |= bit_arch_##name;                                           \
  90       break;                                                            \
  91     }
  92
  93 /* Enable/disable an ARCH feature NAME.  Enable an ARCH feature only
  94    if the CPU feature NEED is also enabled.  */
  95 # define CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH(f, cpu_features, name,    \
  96                                               need, disable, len)       \
  97   _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);        \
  98   if (!DEFAULT_MEMCMP (f, #name, len))                                  \
  99     {                                                                   \
 100       if (disable)                                                      \
 101         cpu_features->feature[index_arch_##name]                        \
 102           &= ~bit_arch_##name;                                          \
 103       else if (CPU_FEATURES_CPU_P (cpu_features, need))                 \
 104         cpu_features->feature[index_arch_##name]                        \
 105           |= bit_arch_##name;                                           \
 106       break;                                                            \
 107     }
 108
 109 attribute_hidden
 110 void
 111 TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
 112 {
 113   /* The current IFUNC selection is based on microbenchmarks in glibc.
 114      It should give the best performance for most workloads.  But other
 115      choices may have better performance for a particular workload or on
 116      the hardware which wasn't available when the selection was made.
 117      The environment variable:
 118
 119      GLIBC_TUNABLES=glibc.tune.hwcaps=-xxx,yyy,-zzz,....
 120
 121      can be used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature
 122      yyy and zzz, where the feature name is case-sensitive and has to
 123      match the ones in cpu-features.h.  It can be used by glibc developers
 124      to tune for a new processor or override the IFUNC selection to
 125      improve performance for a particular workload.
 126
 127      NOTE: the IFUNC selection may change over time.  Please check all
 128      multiarch implementations when experimenting.  */
 129
 130   const char *p = valp->strval;
 131   struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
 132   size_t len;
 133
 134   do
 135     {
 136       const char *c, *n;
 137       bool disable;
 138       size_t nl;
 139
 140       for (c = p; *c != ','; c++)
 141         if (*c == '\0')
 142           break;
 143
 144       len = c - p;
 145       disable = *p == '-';
 146       if (disable)
 147         {
 148           n = p + 1;
 149           nl = len - 1;
 150         }
 151       else
 152         {
 153           n = p;
 154           nl = len;
 155         }
 156       switch (nl)
 157         {
 158         default:
 159           break;
 160         case 3:
 161           if (disable)
 162             {
 163               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX, 3);
 164               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CX8, 3);
 165               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA, 3);
 166               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, HTT, 3);
 167               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, IBT, 3);
 168               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, RTM, 3);
 169             }
 170           break;
 171         case 4:
 172           if (disable)
 173             {
 174               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX2, 4);
 175               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI1, 4);
 176               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI2, 4);
 177               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CMOV, 4);
 178               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, ERMS, 4);
 179               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA4, 4);
 180               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE2, 4);
 181               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, I586, 4);
 182               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, I686, 4);
 183             }
 184           break;
 185         case 5:
 186           if (disable)
 187             {
 188               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, LZCNT, 5);
 189               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, MOVBE, 5);
 190               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SHSTK, 5);
 191               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSSE3, 5);
 192             }
 193           break;
 194         case 6:
 195           if (disable)
 196             {
 197               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6);
 198               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6);
 199               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6);
 200             }
 201           break;
 202         case 7:
 203           if (disable)
 204             {
 205               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512F, 7);
 206               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, OSXSAVE, 7);
 207             }
 208           break;
 209         case 8:
 210           if (disable)
 211             {
 212               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512CD, 8);
 213               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512BW, 8);
 214               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512DQ, 8);
 215               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512ER, 8);
 216               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512PF, 8);
 217               CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512VL, 8);
 218             }
 219           CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Slow_BSF,
 220                                        disable, 8);
 221           break;
 222         case 10:
 223           if (disable)
 224             {
 225               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, AVX_Usable,
 226                                           10);
 227               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, FMA_Usable,
 228                                           10);
 229             }
 230           break;
 231         case 11:
 232           if (disable)
 233             {
 234               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, AVX2_Usable,
 235                                           11);
 236               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, FMA4_Usable,
 237                                           11);
 238             }
 239           CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Prefer_ERMS,
 240                                        disable, 11);
 241           CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH (n, cpu_features,
 242                                                 Slow_SSE4_2, SSE4_2,
 243                                                 disable, 11);
 244           break;
 245         case 13:
 246           if (disable)
 247             {
 248               /* Update xsave_state_size to XSAVE state size.  */
 249               cpu_features->xsave_state_size
 250                 = cpu_features->xsave_state_full_size;
 251               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features,
 252                                           XSAVEC_Usable, 13);
 253             }
 254           break;
 255         case 14:
 256           if (disable)
 257             {
 258               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features,
 259                                           AVX512F_Usable, 14);
 260             }
 261           break;
 262         case 15:
 263           if (disable)
 264             {
 265               CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features,
 266                                           AVX512DQ_Usable, 15);
 267             }
 268           CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Fast_Rep_String,
 269                                        disable, 15);
 270           break;
 271         case 16:
 272             {
 273               CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
 274                 (n, cpu_features, Prefer_No_AVX512, AVX512F_Usable,
 275                  disable, 16);
 276             }
 277           break;
 278         case 18:
 279             {
 280               CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features,
 281                                            Fast_Copy_Backward, disable,
 282                                            18);
 283             }
 284           break;
 285         case 19:
 286             {
 287               CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features,
 288                                            Fast_Unaligned_Load, disable,
 289                                            19);
 290               CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features,
 291                                            Fast_Unaligned_Copy, disable,
 292                                            19);
 293             }
 294           break;
 295         case 20:
 296             {
 297               CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
 298                 (n, cpu_features, Prefer_No_VZEROUPPER, AVX_Usable,
 299                  disable, 20);
 300             }
 301           break;
 302         case 21:
 303             {
 304               CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features,
 305                                            Prefer_MAP_32BIT_EXEC, disable,
 306                                            21);
 307             }
 308           break;
 309         case 23:
 310             {
 311               CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
 312                 (n, cpu_features, AVX_Fast_Unaligned_Load, AVX_Usable,
 313                  disable, 23);
 314             }
 315           break;
 316         case 24:
 317             {
 318               CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
 319                 (n, cpu_features, MathVec_Prefer_No_AVX512,
 320                  AVX512F_Usable, disable, 24);
 321             }
 322           break;
 323         case 26:
 324             {
 325               CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH
 326                 (n, cpu_features, Prefer_PMINUB_for_stringop, SSE2,
 327                  disable, 26);
 328             }
 329           break;
 330         }
 331       p += len + 1;
 332     }
 333   while (*p != '\0');
 334 }
 335 #endif