sysdeps/x86/cacheinfo.h

   1 /* x86 cache info.
   2    Copyright (C) 2020-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <unistd.h>
  21 #include <cpuid.h>
  22 #include <cpu-features.h>
  23
  24 #if HAVE_TUNABLES
  25 # define TUNABLE_NAMESPACE cpu
  26 # include <unistd.h>            /* Get STDOUT_FILENO for _dl_printf.  */
  27 # include <elf/dl-tunables.h>
  28 #endif
  29
  30 #if IS_IN (libc)
  31 /* Data cache size for use in memory and string routines, typically
  32    L1 size, rounded to multiple of 256 bytes.  */
  33 long int __x86_data_cache_size_half attribute_hidden = 32 * 1024 / 2;
  34 long int __x86_data_cache_size attribute_hidden = 32 * 1024;
  35 /* Shared cache size for use in memory and string routines, typically
  36    L2 or L3 size, rounded to multiple of 256 bytes.  */
  37 long int __x86_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2;
  38 long int __x86_shared_cache_size attribute_hidden = 1024 * 1024;
  39
  40 /* Threshold to use non temporal store.  */
  41 long int __x86_shared_non_temporal_threshold attribute_hidden;
  42
  43 /* Threshold to use Enhanced REP MOVSB.  */
  44 long int __x86_rep_movsb_threshold attribute_hidden = 2048;
  45
  46 /* Threshold to use Enhanced REP STOSB.  */
  47 long int __x86_rep_stosb_threshold attribute_hidden = 2048;
  48
  49 /* Threshold to stop using Enhanced REP MOVSB.  */
  50 long int __x86_rep_movsb_stop_threshold attribute_hidden;
  51
  52 /* A bit-wise OR of string/memory requirements for optimal performance
  53    e.g. X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB.  These bits
  54    are used at runtime to tune implementation behavior.  */
  55 int __x86_string_control attribute_hidden;
  56
  57 static void
  58 init_cacheinfo (void)
  59 {
  60   const struct cpu_features *cpu_features = __get_cpu_features ();
  61   long int data = cpu_features->data_cache_size;
  62   /* Round data cache size to multiple of 256 bytes.  */
  63   data = data & ~255L;
  64   if (data > 0)
  65     {
  66       __x86_data_cache_size_half = data / 2;
  67       __x86_data_cache_size = data;
  68     }
  69
  70   long int shared = cpu_features->shared_cache_size;
  71   /* Round shared cache size to multiple of 256 bytes.  */
  72   shared = shared & ~255L;
  73   if (shared > 0)
  74     {
  75       __x86_shared_cache_size_half = shared / 2;
  76       __x86_shared_cache_size = shared;
  77     }
  78
  79   __x86_shared_non_temporal_threshold
  80     = cpu_features->non_temporal_threshold;
  81
  82   __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
  83   __x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
  84   __x86_rep_movsb_stop_threshold =  cpu_features->rep_movsb_stop_threshold;
  85
  86   if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_Short_Distance_REP_MOVSB))
  87     __x86_string_control
  88       |= X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB;
  89 }
  90 #endif