diff options
Diffstat (limited to 'sysdeps/x86/cpu-tunables.c')
| -rw-r--r-- | sysdeps/x86/cpu-tunables.c | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c new file mode 100644 index 0000000000..9258fb41de --- /dev/null +++ b/sysdeps/x86/cpu-tunables.c @@ -0,0 +1,330 @@ +/* x86 CPU feature tuning. + This file is part of the GNU C Library. + Copyright (C) 2017 Free Software Foundation, Inc. + + 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 + <http://www.gnu.org/licenses/>. */ + +#if HAVE_TUNABLES +# define TUNABLE_NAMESPACE tune +# include <stdbool.h> +# include <stdint.h> +# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */ +# include <elf/dl-tunables.h> +# include <string.h> +# include <cpu-features.h> +# include <ldsodefs.h> + +/* We can't use IFUNC memcmp nor strlen in init_cpu_features from libc.a + since IFUNC must be set up by init_cpu_features. */ +# if defined USE_MULTIARCH && !defined SHARED +# ifdef __x86_64__ +# define DEFAULT_MEMCMP __memcmp_sse2 +# define DEFAULT_STRLEN __strlen_sse2 +# else +# define DEFAULT_MEMCMP __memcmp_ia32 +# define DEFAULT_STRLEN strlen +# endif +extern __typeof (memcmp) DEFAULT_MEMCMP; +extern __typeof (strlen) DEFAULT_STRLEN; +# else +# define DEFAULT_MEMCMP memcmp +# define DEFAULT_STRLEN strlen +# endif + +# define CHECK_GLIBC_IFUNC_CPU_OFF(f, cpu_features, name, len) \ + _Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \ + if (!DEFAULT_MEMCMP (f, #name, len)) \ + { \ + cpu_features->cpuid[index_cpu_##name].reg_##name \ + &= ~bit_cpu_##name; \ + break; \ + } + +/* Disable an ARCH feature NAME. We don't enable an ARCH feature which + isn't available. */ +# define CHECK_GLIBC_IFUNC_ARCH_OFF(f, cpu_features, name, len) \ + _Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \ + if (!DEFAULT_MEMCMP (f, #name, len)) \ + { \ + cpu_features->feature[index_arch_##name] \ + &= ~bit_arch_##name; \ + break; \ + } + +/* Enable/disable an ARCH feature NAME. */ +# define CHECK_GLIBC_IFUNC_ARCH_BOTH(f, cpu_features, name, disable, \ + len) \ + _Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \ + if (!DEFAULT_MEMCMP (f, #name, len)) \ + { \ + if (disable) \ + cpu_features->feature[index_arch_##name] \ + &= ~bit_arch_##name; \ + else \ + cpu_features->feature[index_arch_##name] \ + |= bit_arch_##name; \ + break; \ + } + +/* Enable/disable an ARCH feature NAME. Enable an ARCH feature only + if the ARCH feature NEED is also enabled. */ +# define CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH(f, cpu_features, name, \ + need, disable, len) \ + _Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \ + if (!DEFAULT_MEMCMP (f, #name, len)) \ + { \ + if (disable) \ + cpu_features->feature[index_arch_##name] \ + &= ~bit_arch_##name; \ + else if (CPU_FEATURES_ARCH_P (cpu_features, need)) \ + cpu_features->feature[index_arch_##name] \ + |= bit_arch_##name; \ + break; \ + } + +/* Enable/disable an ARCH feature NAME. Enable an ARCH feature only + if the CPU feature NEED is also enabled. */ +# define CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH(f, cpu_features, name, \ + need, disable, len) \ + _Static_assert (sizeof (#name) - 1 == len, #name " != " #len); \ + if (!DEFAULT_MEMCMP (f, #name, len)) \ + { \ + if (disable) \ + cpu_features->feature[index_arch_##name] \ + &= ~bit_arch_##name; \ + else if (CPU_FEATURES_CPU_P (cpu_features, need)) \ + cpu_features->feature[index_arch_##name] \ + |= bit_arch_##name; \ + break; \ + } + +attribute_hidden +void +TUNABLE_CALLBACK (set_ifunc) (tunable_val_t *valp) +{ + /* The current IFUNC selection is based on microbenchmarks in glibc. + It should give the best performance for most workloads. But other + choices may have better performance for a particular workload or on + the hardware which wasn't available when the selection was made. + The environment variable, GLIBC_IFUNC=-xxx,yyy,-zzz...., can be + used to enable CPU/ARCH feature yyy, disable CPU/ARCH feature yyy + and zzz, where the feature name is case-sensitive and has to match + the ones in cpu-features.h. It can be used by glibc developers to + tune for a new processor or override the IFUNC selection to improve + performance for a particular workload. + + Since all CPU/ARCH features are hardware optimizations without + security implication, except for Prefer_MAP_32BIT_EXEC, which can + only be disabled, we check GLIBC_IFUNC for programs, including + set*id ones. + + NOTE: the IFUNC selection may change over time. Please check all + multiarch implementations when experimenting. */ + + const char *p = valp->strval; + struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features); + const char *end = p + DEFAULT_STRLEN (p); + size_t len; + + do + { + const char *c, *n; + bool disable; + size_t nl; + + for (c = p; *c != ','; c++) + if (c >= end) + break; + + len = c - p; + disable = *p == '-'; + if (disable) + { + n = p + 1; + nl = len - 1; + } + else + { + n = p; + nl = len; + } + switch (nl) + { + default: + break; + case 3: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX, 3); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CX8, 3); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA, 3); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, HTT, 3); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, RTM, 3); + } + break; + case 4: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX2, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI1, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, BMI2, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, CMOV, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, ERMS, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, FMA4, 4); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE2, 4); + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, I586, 4); + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, I686, 4); + } + break; + case 5: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, LZCNT, 5); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, MOVBE, 5); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSSE3, 5); + } + break; + case 6: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, POPCNT, 6); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_1, 6); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, SSE4_2, 6); + } + break; + case 7: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512F, 7); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, OSXSAVE, 7); + } + break; + case 8: + if (disable) + { + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512CD, 8); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512BW, 8); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512DQ, 8); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512ER, 8); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512PF, 8); + CHECK_GLIBC_IFUNC_CPU_OFF (n, cpu_features, AVX512VL, 8); + } + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Slow_BSF, + disable, 8); + break; + case 10: + if (disable) + { + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, AVX_Usable, + 10); + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, FMA_Usable, + 10); + } + break; + case 11: + if (disable) + { + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, AVX2_Usable, + 11); + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, FMA4_Usable, + 11); + } + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Prefer_ERMS, + disable, 11); + CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH (n, cpu_features, + Slow_SSE4_2, SSE4_2, + disable, 11); + break; + case 14: + if (disable) + { + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, + AVX512F_Usable, 14); + } + break; + case 15: + if (disable) + { + CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features, + AVX512DQ_Usable, 15); + } + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, Fast_Rep_String, + disable, 15); + break; + case 16: + { + CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH + (n, cpu_features, Prefer_No_AVX512, AVX512F_Usable, + disable, 16); + } + break; + case 18: + { + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, + Fast_Copy_Backward, disable, + 18); + } + break; + case 19: + { + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, + Fast_Unaligned_Load, disable, + 19); + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, + Fast_Unaligned_Copy, disable, + 19); + } + break; + case 20: + { + CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH + (n, cpu_features, Prefer_No_VZEROUPPER, AVX_Usable, + disable, 20); + } + break; + case 21: + { + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, + Prefer_MAP_32BIT_EXEC, disable, + 21); + } + break; + case 23: + { + CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH + (n, cpu_features, AVX_Fast_Unaligned_Load, AVX_Usable, + disable, 23); + } + break; + case 26: + { + CHECK_GLIBC_IFUNC_ARCH_NEED_CPU_BOTH + (n, cpu_features, Prefer_PMINUB_for_stringop, SSE2, + disable, 26); + } + break; + case 27: + { + CHECK_GLIBC_IFUNC_ARCH_BOTH (n, cpu_features, + Use_dl_runtime_resolve_slow, + disable, 27); + } + break; + } + p += len + 1; + } + while (p < end); +} +#endif |