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