diff options
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/x86/dl-cacheinfo.h | 79 |
1 files changed, 48 insertions, 31 deletions
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h index 637b5a022d..6e7d0197a7 100644 --- a/sysdeps/x86/dl-cacheinfo.h +++ b/sysdeps/x86/dl-cacheinfo.h @@ -478,7 +478,7 @@ handle_zhaoxin (int name) } static void -get_common_cache_info (long int *shared_ptr, unsigned int *threads_ptr, +get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, unsigned int *threads_ptr, long int core) { unsigned int eax; @@ -497,6 +497,7 @@ get_common_cache_info (long int *shared_ptr, unsigned int *threads_ptr, unsigned int family = cpu_features->basic.family; unsigned int model = cpu_features->basic.model; long int shared = *shared_ptr; + long int shared_per_thread = *shared_per_thread_ptr; unsigned int threads = *threads_ptr; bool inclusive_cache = true; bool support_count_mask = true; @@ -512,6 +513,7 @@ get_common_cache_info (long int *shared_ptr, unsigned int *threads_ptr, /* Try L2 otherwise. */ level = 2; shared = core; + shared_per_thread = core; threads_l2 = 0; threads_l3 = -1; } @@ -668,29 +670,28 @@ get_common_cache_info (long int *shared_ptr, unsigned int *threads_ptr, } else { -intel_bug_no_cache_info: - /* Assume that all logical threads share the highest cache - level. */ - threads - = ((cpu_features->features[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; + intel_bug_no_cache_info: + /* Assume that all logical threads share the highest cache + level. */ + threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16) + & 0xff); + + /* Get per-thread size of highest level cache. */ + if (shared_per_thread > 0 && threads > 0) + shared_per_thread /= threads; + } } /* Account for non-inclusive L2 and L3 caches. */ if (!inclusive_cache) { if (threads_l2 > 0) - core /= threads_l2; + shared_per_thread += core / threads_l2; shared += core; } *shared_ptr = shared; + *shared_per_thread_ptr = shared_per_thread; *threads_ptr = threads; } @@ -704,6 +705,7 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) int max_cpuid_ex; long int data = -1; long int shared = -1; + long int shared_per_thread = -1; long int core = -1; unsigned int threads = 0; unsigned long int level1_icache_size = -1; @@ -724,6 +726,7 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) 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); + shared_per_thread = shared; level1_icache_size = handle_intel (_SC_LEVEL1_ICACHE_SIZE, cpu_features); @@ -747,13 +750,14 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) level4_cache_size = handle_intel (_SC_LEVEL4_CACHE_SIZE, cpu_features); - get_common_cache_info (&shared, &threads, core); + get_common_cache_info (&shared, &shared_per_thread, &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); + shared_per_thread = shared; level1_icache_size = handle_zhaoxin (_SC_LEVEL1_ICACHE_SIZE); level1_icache_linesize = handle_zhaoxin (_SC_LEVEL1_ICACHE_LINESIZE); @@ -767,13 +771,14 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) level3_cache_assoc = handle_zhaoxin (_SC_LEVEL3_CACHE_ASSOC); level3_cache_linesize = handle_zhaoxin (_SC_LEVEL3_CACHE_LINESIZE); - get_common_cache_info (&shared, &threads, core); + get_common_cache_info (&shared, &shared_per_thread, &threads, core); } else if (cpu_features->basic.kind == arch_kind_amd) { data = handle_amd (_SC_LEVEL1_DCACHE_SIZE); core = handle_amd (_SC_LEVEL2_CACHE_SIZE); shared = handle_amd (_SC_LEVEL3_CACHE_SIZE); + shared_per_thread = shared; level1_icache_size = handle_amd (_SC_LEVEL1_ICACHE_SIZE); level1_icache_linesize = handle_amd (_SC_LEVEL1_ICACHE_LINESIZE); @@ -791,8 +796,11 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) __cpuid (0x80000000, max_cpuid_ex, ebx, ecx, edx); if (shared <= 0) - /* No shared L3 cache. All we have is the L2 cache. */ - shared = core; + { + /* No shared L3 cache. All we have is the L2 cache. */ + shared = core; + shared_per_thread = core; + } else { /* Figure out the number of logical threads that share L3. */ @@ -816,7 +824,7 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) /* Cap usage of highest cache level to the number of supported threads. */ if (threads > 0) - shared /= threads; + shared_per_thread /= threads; /* Get shared cache per ccx for Zen architectures. */ if (cpu_features->basic.family >= 0x17) @@ -827,12 +835,13 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) __cpuid_count (0x8000001D, 0x3, eax, ebx, ecx, edx); unsigned int threads_per_ccx = ((eax >> 14) & 0xfff) + 1; - shared *= threads_per_ccx; + shared_per_thread *= threads_per_ccx; } else { /* Account for exclusive L2 and L3 caches. */ shared += core; + shared_per_thread += core; } } } @@ -850,17 +859,25 @@ dl_init_cacheinfo (struct cpu_features *cpu_features) cpu_features->level3_cache_linesize = level3_cache_linesize; cpu_features->level4_cache_size = level4_cache_size; - /* 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. */ - unsigned long int non_temporal_threshold = shared * 3 / 4; + /* The default setting for the non_temporal threshold is 1/4 of size + of the chip's cache. For most Intel and AMD processors with an + initial release date between 2017 and 2023, a thread's typical + share of the cache is from 18-64MB. Using the 1/4 L3 is meant to + estimate the point where non-temporal stores begin out-competing + REP MOVSB. As well the point where the fact that non-temporal + stores are forced back to main memory would already occurred to the + majority of the lines in the copy. Note, concerns about the + entire L3 cache being evicted by the copy are mostly alleviated + by the fact that modern HW detects streaming patterns and + provides proper LRU hints so that the maximum thrashing + capped at 1/associativity. */ + unsigned long int non_temporal_threshold = shared / 4; + /* If no ERMS, we use the per-thread L3 chunking. Normal cacheable stores run + a higher risk of actually thrashing the cache as they don't have a HW LRU + hint. As well, their performance in highly parallel situations is + noticeably worse. */ + if (!CPU_FEATURE_USABLE_P (cpu_features, ERMS)) + non_temporal_threshold = shared_per_thread * 3 / 4; /* SIZE_MAX >> 4 because memmove-vec-unaligned-erms right-shifts the value of 'x86_non_temporal_threshold' by `LOG_4X_MEMCPY_THRESH` (4) and it is best if that operation cannot overflow. Minimum of 0x4040 (16448) because the |