1 /* x86 cache info. 2 Copyright (C) 2020-2022 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 init_cacheinfo(void)58init_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 91