| 1 | /* x86 cache info. |
|---|---|
| 2 | Copyright (C) 2020-2024 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 |
| 89 |