From bd6d7b299575a88d69246c70fc3ad8a68235deb5 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 23 May 2017 20:22:13 -0700
Subject: [PATCH] Add TUNABLES to control IFUNC selection and cache sizes
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 at 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 override the IFUNC selection to tune
for a new processor or improve performance for a particular workload.
It isn't intended for normal end users.
NOTE: the IFUNC selection may change over time. Please check all
multiarch implementations when experimenting.
2017-05-27 H.J. Lu <hongjiu.lu@intel.com>
Erich Elsen <eriche@google.com>
* elf/dl-tunables.list: Add a "tune" namespace.
* sysdeps/unix/sysv/linux/x86/dl-sysdep.c: New file.
* sysdeps/x86/cpu-tunables.c: Likewise.
* sysdeps/x86/cacheinfo.c (TUNABLE_NAMESPACE): New.
Include <elf/dl-tunables.h> for TUNABLES is on.
Include <string.h> and <stdlib.h> if TUNABLES is off.
(__environ): New.
(init_cacheinfo): Use TUNABLES to set data cache size, shared
cache size and non temporal threshold if TUNABLES is on. Search
the environment strings to set data cache size, shared cache
size and non temporal threshold if TUNABLES is off.
* sysdeps/x86/cpu-features.c (TUNABLE_NAMESPACE): New.
(DL_TUNABLE_CALLBACK (set_ifunc)): Likewise.
Include <elf/dl-tunables.h> for TUNABLES is on.
Include <string.h> and <unistd.h> if TUNABLES is off.
(__environ): New.
(_dl_x86_set_ifunc): Likewise.
(init_cpu_features): Use TUNABLE_SET_VAL_WITH_CALLBACK if
TUNABLES is on. Call _dl_x86_set_ifunc for GLIBC_IFUNC= if
TUNABLES is off.
* sysdeps/x86/cpu-features.h (DEFAULT_MEMCMP): New.
---
elf/dl-tunables.list | 22 +++
sysdeps/unix/sysv/linux/x86/dl-sysdep.c | 21 +++
sysdeps/x86/cacheinfo.c | 54 +++++-
sysdeps/x86/cpu-features.c | 36 ++++
sysdeps/x86/cpu-features.h | 12 ++
sysdeps/x86/cpu-tunables.c | 322 ++++++++++++++++++++++++++++++++
6 files changed, 466 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/unix/sysv/linux/x86/dl-sysdep.c
create mode 100644 sysdeps/x86/cpu-tunables.c
@@ -77,4 +77,26 @@ glibc {
security_level: SXID_IGNORE
}
}
+ tune {
+ ifunc {
+ type: STRING
+ env_alias: GLIBC_IFUNC
+ security_level: SXID_IGNORE
+ }
+ non_temporal_threshold {
+ type: SIZE_T
+ env_alias: GLIBC_NON_TEMPORAL_THRESHOLD
+ security_level: SXID_IGNORE
+ }
+ data_cache_size {
+ type: SIZE_T
+ env_alias: GLIBC_DATA_CACHE_SIZE
+ security_level: SXID_IGNORE
+ }
+ shared_cache_size {
+ type: SIZE_T
+ env_alias: GLIBC_SHARED_CACHE_SIZE
+ security_level: SXID_IGNORE
+ }
+ }
}
new file mode 100644
@@ -0,0 +1,21 @@
+/* Operating system support for run-time dynamic linker. X86 version.
+ Copyright (C) 2017 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+#include <sysdeps/x86/cpu-tunables.c>
+#include <sysdeps/unix/sysv/linux/dl-sysdep.c>
@@ -25,6 +25,15 @@
#include <cpuid.h>
#include <init-arch.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE tune
+# include <elf/dl-tunables.h>
+#else
+# include <string.h>
+# include <stdlib.h>
+extern char **__environ;
+#endif
+
static const struct intel_02_cache_info
{
unsigned char idx;
@@ -752,6 +761,43 @@ intel_bug_no_cache_info:
#endif
}
+ /* Data cache size for use in memory and string routines, typically
+ L1 size. */
+ long int data_cache_size = 0;
+ /* Shared cache size for use in memory and string routines, typically
+ L2 or L3 size. */
+ long int shared_cache_size = 0;
+ /* Threshold to use non temporal store. */
+ long int non_temporal_threshold = 0;
+
+#if HAVE_TUNABLES
+ TUNABLE_SET_VAL (non_temporal_threshold, &non_temporal_threshold);
+ TUNABLE_SET_VAL (data_cache_size, &data_cache_size);
+ TUNABLE_SET_VAL (shared_cache_size, &shared_cache_size);
+#else
+ if (__glibc_likely (__environ != NULL)
+ && !__builtin_expect (__libc_enable_secure, 0))
+ {
+ char **runp = __environ;
+ char *envline;
+
+ while (*runp != NULL)
+ {
+ envline = *runp;
+ if (!memcmp (envline, "GLIBC_NON_TEMPORAL_THRESHOLD=", 29))
+ non_temporal_threshold = strtol (&envline[29], NULL, 0);
+ else if (!memcmp (envline, "GLIBC_DATA_CACHE_SIZE=", 22))
+ data_cache_size = strtol (&envline[22], NULL, 0);
+ else if (!memcmp (envline, "GLIBC_SHARED_CACHE_SIZE=", 24))
+ shared_cache_size = strtol (&envline[24], NULL, 0);
+ runp++;
+ }
+ }
+#endif
+
+ if (data_cache_size != 0)
+ data = data_cache_size;
+
if (data > 0)
{
__x86_raw_data_cache_size_half = data / 2;
@@ -762,6 +808,9 @@ intel_bug_no_cache_info:
__x86_data_cache_size = data;
}
+ if (shared_cache_size != 0)
+ shared = shared_cache_size;
+
if (shared > 0)
{
__x86_raw_shared_cache_size_half = shared / 2;
@@ -775,7 +824,10 @@ intel_bug_no_cache_info:
/* The large memcpy micro benchmark in glibc shows that 6 times of
shared cache size is the approximate value above which non-temporal
store becomes faster. */
- __x86_shared_non_temporal_threshold = __x86_shared_cache_size * 6;
+ __x86_shared_non_temporal_threshold
+ = (non_temporal_threshold != 0
+ ? non_temporal_threshold
+ : __x86_shared_cache_size * 6);
}
#endif
@@ -20,6 +20,19 @@
#include <cpu-features.h>
#include <dl-hwcap.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE tune
+# include <elf/dl-tunables.h>
+
+extern void DL_TUNABLE_CALLBACK (set_ifunc) (tunable_val_t *)
+ attribute_hidden;
+#else
+# include <string.h>
+# include <unistd.h>
+extern char **__environ attribute_hidden;
+extern void _dl_x86_set_ifunc (const char *) attribute_hidden;
+#endif
+
static void
get_common_indeces (struct cpu_features *cpu_features,
unsigned int *family, unsigned int *model,
@@ -312,6 +325,29 @@ no_cpuid:
cpu_features->model = model;
cpu_features->kind = kind;
+#if HAVE_TUNABLES
+ TUNABLE_SET_VAL_WITH_CALLBACK (ifunc, NULL, set_ifunc);
+#else
+ if (__glibc_likely (__environ != NULL)
+ && !__builtin_expect (__libc_enable_secure, 0))
+ {
+ char **runp = __environ;
+ char *envline;
+
+ while (*runp != NULL)
+ {
+ envline = *runp;
+ if (!DEFAULT_MEMCMP (envline, "GLIBC_IFUNC=",
+ sizeof ("GLIBC_IFUNC=") - 1))
+ {
+ _dl_x86_set_ifunc (envline + sizeof ("GLIBC_IFUNC=") - 1);
+ break;
+ }
+ runp++;
+ }
+ }
+#endif
+
#if IS_IN (rtld)
/* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86. */
GLRO(dl_platform) = NULL;
@@ -227,6 +227,18 @@ extern const struct cpu_features *__get_cpu_features (void)
# define __get_cpu_features() (&GLRO(dl_x86_cpu_features))
# endif
+/* We can't use IFUNC memcmp 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
+# else
+# define DEFAULT_MEMCMP __memcmp_ia32
+# endif
+extern __typeof (memcmp) DEFAULT_MEMCMP;
+# else
+# define DEFAULT_MEMCMP memcmp
+# endif
/* Only used directly in cpu-features.c. */
# define CPU_FEATURES_CPU_P(ptr, name) \
new file mode 100644
@@ -0,0 +1,322 @@
+/* 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/>. */
+
+#include <string.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE tune
+# include <elf/dl-tunables.h>
+#endif
+#include <cpu-features.h>
+#include <ldsodefs.h>
+
+#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; \
+ }
+
+#if HAVE_TUNABLES
+static
+#else
+attribute_hidden
+#endif
+void
+_dl_x86_set_ifunc (const char *p)
+{
+ /* 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. */
+
+ struct cpu_features *cpu_features = &GLRO(dl_x86_cpu_features);
+ const char *end = p + 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);
+}
+
+#if HAVE_TUNABLES
+attribute_hidden
+void
+DL_TUNABLE_CALLBACK (set_ifunc) (tunable_val_t *valp)
+{
+ _dl_x86_set_ifunc (valp->strval);
+}
+#endif
--
2.9.4