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Diffstat (limited to 'sysdeps/x86/cacheinfo.h')
| -rw-r--r-- | sysdeps/x86/cacheinfo.h | 413 |
1 files changed, 413 insertions, 0 deletions
diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h new file mode 100644 index 0000000000..7f342fdc23 --- /dev/null +++ b/sysdeps/x86/cacheinfo.h @@ -0,0 +1,413 @@ +/* x86 cache info. + Copyright (C) 2020 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <assert.h> +#include <unistd.h> + +/* Data cache size for use in memory and string routines, typically + L1 size, rounded to multiple of 256 bytes. */ +long int __x86_data_cache_size_half attribute_hidden = 32 * 1024 / 2; +long int __x86_data_cache_size attribute_hidden = 32 * 1024; +/* Similar to __x86_data_cache_size_half, but not rounded. */ +long int __x86_raw_data_cache_size_half attribute_hidden = 32 * 1024 / 2; +/* Similar to __x86_data_cache_size, but not rounded. */ +long int __x86_raw_data_cache_size attribute_hidden = 32 * 1024; +/* Shared cache size for use in memory and string routines, typically + L2 or L3 size, rounded to multiple of 256 bytes. */ +long int __x86_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2; +long int __x86_shared_cache_size attribute_hidden = 1024 * 1024; +/* Similar to __x86_shared_cache_size_half, but not rounded. */ +long int __x86_raw_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2; +/* Similar to __x86_shared_cache_size, but not rounded. */ +long int __x86_raw_shared_cache_size attribute_hidden = 1024 * 1024; + +/* Threshold to use non temporal store. */ +long int __x86_shared_non_temporal_threshold attribute_hidden; + +/* Threshold to use Enhanced REP MOVSB. */ +long int __x86_rep_movsb_threshold attribute_hidden = 2048; + +/* Threshold to use Enhanced REP STOSB. */ +long int __x86_rep_stosb_threshold attribute_hidden = 2048; + +static void +get_common_cache_info (long int *shared_ptr, unsigned int *threads_ptr, + long int core) +{ + unsigned int eax; + unsigned int ebx; + unsigned int ecx; + unsigned int edx; + + /* Number of logical processors sharing L2 cache. */ + int threads_l2; + + /* Number of logical processors sharing L3 cache. */ + int threads_l3; + + const struct cpu_features *cpu_features = __get_cpu_features (); + int max_cpuid = cpu_features->basic.max_cpuid; + unsigned int family = cpu_features->basic.family; + unsigned int model = cpu_features->basic.model; + long int shared = *shared_ptr; + unsigned int threads = *threads_ptr; + bool inclusive_cache = true; + bool support_count_mask = true; + + /* Try L3 first. */ + unsigned int level = 3; + + if (cpu_features->basic.kind == arch_kind_zhaoxin && family == 6) + support_count_mask = false; + + if (shared <= 0) + { + /* Try L2 otherwise. */ + level = 2; + shared = core; + threads_l2 = 0; + threads_l3 = -1; + } + else + { + threads_l2 = 0; + threads_l3 = 0; + } + + /* A value of 0 for the HTT bit indicates there is only a single + logical processor. */ + if (HAS_CPU_FEATURE (HTT)) + { + /* Figure out the number of logical threads that share the + highest cache level. */ + if (max_cpuid >= 4) + { + int i = 0; + + /* Query until cache level 2 and 3 are enumerated. */ + int check = 0x1 | (threads_l3 == 0) << 1; + do + { + __cpuid_count (4, i++, eax, ebx, ecx, edx); + + /* There seems to be a bug in at least some Pentium Ds + which sometimes fail to iterate all cache parameters. + Do not loop indefinitely here, stop in this case and + assume there is no such information. */ + if (cpu_features->basic.kind == arch_kind_intel + && (eax & 0x1f) == 0 ) + goto intel_bug_no_cache_info; + + switch ((eax >> 5) & 0x7) + { + default: + break; + case 2: + if ((check & 0x1)) + { + /* Get maximum number of logical processors + sharing L2 cache. */ + threads_l2 = (eax >> 14) & 0x3ff; + check &= ~0x1; + } + break; + case 3: + if ((check & (0x1 << 1))) + { + /* Get maximum number of logical processors + sharing L3 cache. */ + threads_l3 = (eax >> 14) & 0x3ff; + + /* Check if L2 and L3 caches are inclusive. */ + inclusive_cache = (edx & 0x2) != 0; + check &= ~(0x1 << 1); + } + break; + } + } + while (check); + + /* If max_cpuid >= 11, THREADS_L2/THREADS_L3 are the maximum + numbers of addressable IDs for logical processors sharing + the cache, instead of the maximum number of threads + sharing the cache. */ + if (max_cpuid >= 11 && support_count_mask) + { + /* Find the number of logical processors shipped in + one core and apply count mask. */ + i = 0; + + /* Count SMT only if there is L3 cache. Always count + core if there is no L3 cache. */ + int count = ((threads_l2 > 0 && level == 3) + | ((threads_l3 > 0 + || (threads_l2 > 0 && level == 2)) << 1)); + + while (count) + { + __cpuid_count (11, i++, eax, ebx, ecx, edx); + + int shipped = ebx & 0xff; + int type = ecx & 0xff00; + if (shipped == 0 || type == 0) + break; + else if (type == 0x100) + { + /* Count SMT. */ + if ((count & 0x1)) + { + int count_mask; + + /* Compute count mask. */ + asm ("bsr %1, %0" + : "=r" (count_mask) : "g" (threads_l2)); + count_mask = ~(-1 << (count_mask + 1)); + threads_l2 = (shipped - 1) & count_mask; + count &= ~0x1; + } + } + else if (type == 0x200) + { + /* Count core. */ + if ((count & (0x1 << 1))) + { + int count_mask; + int threads_core + = (level == 2 ? threads_l2 : threads_l3); + + /* Compute count mask. */ + asm ("bsr %1, %0" + : "=r" (count_mask) : "g" (threads_core)); + count_mask = ~(-1 << (count_mask + 1)); + threads_core = (shipped - 1) & count_mask; + if (level == 2) + threads_l2 = threads_core; + else + threads_l3 = threads_core; + count &= ~(0x1 << 1); + } + } + } + } + if (threads_l2 > 0) + threads_l2 += 1; + if (threads_l3 > 0) + threads_l3 += 1; + if (level == 2) + { + if (threads_l2) + { + threads = threads_l2; + if (cpu_features->basic.kind == arch_kind_intel + && threads > 2 + && family == 6) + switch (model) + { + case 0x37: + case 0x4a: + case 0x4d: + case 0x5a: + case 0x5d: + /* Silvermont has L2 cache shared by 2 cores. */ + threads = 2; + break; + default: + break; + } + } + } + else if (threads_l3) + threads = threads_l3; + } + else + { +intel_bug_no_cache_info: + /* Assume that all logical threads share the highest cache + level. */ + threads + = ((cpu_features->features[COMMON_CPUID_INDEX_1].cpuid.ebx + >> 16) & 0xff); + } + + /* Cap usage of highest cache level to the number of supported + threads. */ + if (shared > 0 && threads > 0) + shared /= threads; + } + + /* Account for non-inclusive L2 and L3 caches. */ + if (!inclusive_cache) + { + if (threads_l2 > 0) + core /= threads_l2; + shared += core; + } + + *shared_ptr = shared; + *threads_ptr = threads; +} + +static void +init_cacheinfo (void) +{ + /* Find out what brand of processor. */ + unsigned int ebx; + unsigned int ecx; + unsigned int edx; + int max_cpuid_ex; + long int data = -1; + long int shared = -1; + long int core; + unsigned int threads = 0; + const struct cpu_features *cpu_features = __get_cpu_features (); + + /* NB: In libc.so, cpu_features is defined in ld.so and is initialized + by DL_PLATFORM_INIT or IFUNC relocation before init_cacheinfo is + called by IFUNC relocation. In libc.a, init_cacheinfo is called + from init_cpu_features by ARCH_INIT_CPU_FEATURES. */ + assert (cpu_features->basic.kind != arch_kind_unknown); + + if (cpu_features->basic.kind == arch_kind_intel) + { + data = handle_intel (_SC_LEVEL1_DCACHE_SIZE, cpu_features); + core = handle_intel (_SC_LEVEL2_CACHE_SIZE, cpu_features); + shared = handle_intel (_SC_LEVEL3_CACHE_SIZE, cpu_features); + + get_common_cache_info (&shared, &threads, core); + } + else if (cpu_features->basic.kind == arch_kind_zhaoxin) + { + data = handle_zhaoxin (_SC_LEVEL1_DCACHE_SIZE); + core = handle_zhaoxin (_SC_LEVEL2_CACHE_SIZE); + shared = handle_zhaoxin (_SC_LEVEL3_CACHE_SIZE); + + get_common_cache_info (&shared, &threads, core); + } + else if (cpu_features->basic.kind == arch_kind_amd) + { + data = handle_amd (_SC_LEVEL1_DCACHE_SIZE); + long int core = handle_amd (_SC_LEVEL2_CACHE_SIZE); + shared = handle_amd (_SC_LEVEL3_CACHE_SIZE); + + /* Get maximum extended function. */ + __cpuid (0x80000000, max_cpuid_ex, ebx, ecx, edx); + + if (shared <= 0) + /* No shared L3 cache. All we have is the L2 cache. */ + shared = core; + else + { + /* Figure out the number of logical threads that share L3. */ + if (max_cpuid_ex >= 0x80000008) + { + /* Get width of APIC ID. */ + __cpuid (0x80000008, max_cpuid_ex, ebx, ecx, edx); + threads = 1 << ((ecx >> 12) & 0x0f); + } + + if (threads == 0) + { + /* If APIC ID width is not available, use logical + processor count. */ + __cpuid (0x00000001, max_cpuid_ex, ebx, ecx, edx); + + if ((edx & (1 << 28)) != 0) + threads = (ebx >> 16) & 0xff; + } + + /* Cap usage of highest cache level to the number of + supported threads. */ + if (threads > 0) + shared /= threads; + + /* Account for exclusive L2 and L3 caches. */ + shared += core; + } + } + + if (cpu_features->data_cache_size != 0) + data = cpu_features->data_cache_size; + + if (data > 0) + { + __x86_raw_data_cache_size_half = data / 2; + __x86_raw_data_cache_size = data; + /* Round data cache size to multiple of 256 bytes. */ + data = data & ~255L; + __x86_data_cache_size_half = data / 2; + __x86_data_cache_size = data; + } + + if (cpu_features->shared_cache_size != 0) + shared = cpu_features->shared_cache_size; + + if (shared > 0) + { + __x86_raw_shared_cache_size_half = shared / 2; + __x86_raw_shared_cache_size = shared; + /* Round shared cache size to multiple of 256 bytes. */ + shared = shared & ~255L; + __x86_shared_cache_size_half = shared / 2; + __x86_shared_cache_size = shared; + } + + /* The default setting for the non_temporal threshold is 3/4 of one + thread's share of the chip's cache. For most Intel and AMD processors + with an initial release date between 2017 and 2020, a thread's typical + share of the cache is from 500 KBytes to 2 MBytes. Using the 3/4 + threshold leaves 125 KBytes to 500 KBytes of the thread's data + in cache after a maximum temporal copy, which will maintain + in cache a reasonable portion of the thread's stack and other + active data. If the threshold is set higher than one thread's + share of the cache, it has a substantial risk of negatively + impacting the performance of other threads running on the chip. */ + __x86_shared_non_temporal_threshold + = (cpu_features->non_temporal_threshold != 0 + ? cpu_features->non_temporal_threshold + : __x86_shared_cache_size * 3 / 4); + + /* NB: The REP MOVSB threshold must be greater than VEC_SIZE * 8. */ + unsigned int minimum_rep_movsb_threshold; + /* NB: The default REP MOVSB threshold is 2048 * (VEC_SIZE / 16). */ + unsigned int rep_movsb_threshold; + if (CPU_FEATURE_USABLE_P (cpu_features, AVX512F) + && !CPU_FEATURE_PREFERRED_P (cpu_features, Prefer_No_AVX512)) + { + rep_movsb_threshold = 2048 * (64 / 16); + minimum_rep_movsb_threshold = 64 * 8; + } + else if (CPU_FEATURE_PREFERRED_P (cpu_features, + AVX_Fast_Unaligned_Load)) + { + rep_movsb_threshold = 2048 * (32 / 16); + minimum_rep_movsb_threshold = 32 * 8; + } + else + { + rep_movsb_threshold = 2048 * (16 / 16); + minimum_rep_movsb_threshold = 16 * 8; + } + if (cpu_features->rep_movsb_threshold > minimum_rep_movsb_threshold) + __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold; + else + __x86_rep_movsb_threshold = rep_movsb_threshold; + +# if HAVE_TUNABLES + __x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold; +# endif +} |