* V3 [PATCH 0/2] ld.so: Add --list-tunables to print tunable values
@ 2020-10-17 1:02 H.J. Lu via Libc-alpha
2020-10-17 1:02 ` V3 [PATCH 1/2] x86: Move x86 processor cache info to cpu_features H.J. Lu via Libc-alpha
2020-10-17 1:02 ` V3 [PATCH 2/2] ld.so: Add --list-tunables to print tunable values H.J. Lu via Libc-alpha
0 siblings, 2 replies; 3+ messages in thread
From: H.J. Lu via Libc-alpha @ 2020-10-17 1:02 UTC (permalink / raw)
To: libc-alpha; +Cc: Florian Weimer
Tunable values and their minimum/maximum values are invisible to users.
This patch set adds --list-tunables to ld.so to print tunable values
with their minimum and maximum values.
--list-tunables works on i686 and x86-64. Please test --list-tunables on
your native processors. users/hjl/tunable/master branch at:
https://gitlab.com/x86-glibc/glibc/-/commits/users/hjl/tunable/master
contains the same set of patches.
On x86, to make cache info accessible to --list-tunables, they are moved
to cpu_features in ld.so and TUNABLE_SET_WITH_BOUNDS is used to update
tunable bounds.
H.J. Lu (2):
x86: Move x86 processor cache info to cpu_features
ld.so: Add --list-tunables to print tunable values
NEWS | 2 +
elf/Makefile | 8 +
elf/dl-main.h | 2 +-
elf/dl-tunables.c | 36 +++
elf/dl-tunables.h | 2 +
elf/dl-usage.c | 7 +-
elf/rtld.c | 23 ++
manual/tunables.texi | 37 +++
sysdeps/x86/cacheinfo.c | 46 ++-
sysdeps/x86/cacheinfo.h | 384 ++-----------------------
sysdeps/x86/cpu-features.c | 35 +--
sysdeps/x86/dl-cacheinfo.h | 446 +++++++++++++++++++++++++++++
sysdeps/x86/include/cpu-features.h | 22 ++
13 files changed, 652 insertions(+), 398 deletions(-)
--
2.26.2
^ permalink raw reply [flat|nested] 3+ messages in thread
* V3 [PATCH 1/2] x86: Move x86 processor cache info to cpu_features
2020-10-17 1:02 V3 [PATCH 0/2] ld.so: Add --list-tunables to print tunable values H.J. Lu via Libc-alpha
@ 2020-10-17 1:02 ` H.J. Lu via Libc-alpha
2020-10-17 1:02 ` V3 [PATCH 2/2] ld.so: Add --list-tunables to print tunable values H.J. Lu via Libc-alpha
1 sibling, 0 replies; 3+ messages in thread
From: H.J. Lu via Libc-alpha @ 2020-10-17 1:02 UTC (permalink / raw)
To: libc-alpha; +Cc: Florian Weimer
1. Move x86 processor cache info to _dl_x86_cpu_features in ld.so.
2. Update tunable bounds with TUNABLE_SET_WITH_BOUNDS.
3. Move x86 cache info initialization to dl-cacheinfo.h and initialize
x86 cache info in init_cpu_features ().
4. Put x86 cache info for libc in cacheinfo.h, which is included in
libc-start.c in libc.a and is included in cacheinfo.c in libc.so.
---
sysdeps/x86/cacheinfo.c | 46 ++-
sysdeps/x86/cacheinfo.h | 384 ++-----------------------
sysdeps/x86/cpu-features.c | 35 +--
sysdeps/x86/dl-cacheinfo.h | 446 +++++++++++++++++++++++++++++
sysdeps/x86/include/cpu-features.h | 22 ++
5 files changed, 537 insertions(+), 396 deletions(-)
diff --git a/sysdeps/x86/cacheinfo.c b/sysdeps/x86/cacheinfo.c
index 0d2fe3a2fa..e1ea4d5228 100644
--- a/sysdeps/x86/cacheinfo.c
+++ b/sysdeps/x86/cacheinfo.c
@@ -18,11 +18,8 @@
#if IS_IN (libc)
-#include <assert.h>
#include <unistd.h>
-#include <cpuid.h>
#include <ldsodefs.h>
-#include <dl-cacheinfo.h>
/* Get the value of the system variable NAME. */
long int
@@ -30,20 +27,45 @@ attribute_hidden
__cache_sysconf (int name)
{
const struct cpu_features *cpu_features = __get_cpu_features ();
+ switch (name)
+ {
+ case _SC_LEVEL1_ICACHE_SIZE:
+ return cpu_features->level1_icache_size;
- if (cpu_features->basic.kind == arch_kind_intel)
- return handle_intel (name, cpu_features);
+ case _SC_LEVEL1_DCACHE_SIZE:
+ return cpu_features->level1_dcache_size;
- if (cpu_features->basic.kind == arch_kind_amd)
- return handle_amd (name);
+ case _SC_LEVEL1_DCACHE_ASSOC:
+ return cpu_features->level1_dcache_assoc;
- if (cpu_features->basic.kind == arch_kind_zhaoxin)
- return handle_zhaoxin (name);
+ case _SC_LEVEL1_DCACHE_LINESIZE:
+ return cpu_features->level1_dcache_linesize;
- // XXX Fill in more vendors.
+ case _SC_LEVEL2_CACHE_SIZE:
+ return cpu_features->level2_cache_size;
- /* CPU not known, we have no information. */
- return 0;
+ case _SC_LEVEL2_CACHE_ASSOC:
+ return cpu_features->level2_cache_assoc;
+
+ case _SC_LEVEL2_CACHE_LINESIZE:
+ return cpu_features->level2_cache_linesize;
+
+ case _SC_LEVEL3_CACHE_SIZE:
+ return cpu_features->level3_cache_size;
+
+ case _SC_LEVEL3_CACHE_ASSOC:
+ return cpu_features->level3_cache_assoc;
+
+ case _SC_LEVEL3_CACHE_LINESIZE:
+ return cpu_features->level3_cache_linesize;
+
+ case _SC_LEVEL4_CACHE_SIZE:
+ return cpu_features->level4_cache_size;
+
+ default:
+ break;
+ }
+ return -1;
}
# ifdef SHARED
diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h
index 7f342fdc23..5aa40b45b5 100644
--- a/sysdeps/x86/cacheinfo.h
+++ b/sysdeps/x86/cacheinfo.h
@@ -18,7 +18,16 @@
#include <assert.h>
#include <unistd.h>
+#include <cpuid.h>
+#include <cpu-features.h>
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE cpu
+# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
+# include <elf/dl-tunables.h>
+#endif
+
+#if IS_IN (libc)
/* 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;
@@ -45,369 +54,30 @@ 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 ();
+ long int data = cpu_features->data_cache_size;
+ __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;
+
+ long int shared = cpu_features->shared_cache_size;
+ __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;
- /* 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;
+ = cpu_features->non_temporal_threshold;
-# if HAVE_TUNABLES
+ __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
__x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
-# endif
}
+#endif
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index f26deba38d..51c12d89ca 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -16,21 +16,12 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <cpuid.h>
#include <dl-hwcap.h>
#include <libc-pointer-arith.h>
-#if IS_IN (libc) && !defined SHARED
-# include <assert.h>
-# include <unistd.h>
-# include <dl-cacheinfo.h>
-# include <cacheinfo.h>
-#endif
+#include <cacheinfo.h>
+#include <dl-cacheinfo.h>
#if HAVE_TUNABLES
-# define TUNABLE_NAMESPACE cpu
-# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
-# include <elf/dl-tunables.h>
-
extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
attribute_hidden;
@@ -642,24 +633,14 @@ no_cpuid:
cpu_features->basic.model = model;
cpu_features->basic.stepping = stepping;
+ dl_init_cacheinfo (cpu_features);
+
#if HAVE_TUNABLES
TUNABLE_GET (hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
- cpu_features->non_temporal_threshold
- = TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
- cpu_features->rep_movsb_threshold
- = TUNABLE_GET (x86_rep_movsb_threshold, long int, NULL);
- cpu_features->rep_stosb_threshold
- = TUNABLE_GET (x86_rep_stosb_threshold, long int, NULL);
- cpu_features->data_cache_size
- = TUNABLE_GET (x86_data_cache_size, long int, NULL);
- cpu_features->shared_cache_size
- = TUNABLE_GET (x86_shared_cache_size, long int, NULL);
-#endif
-
- /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86. */
-#if !HAVE_TUNABLES && defined SHARED
- /* The glibc.cpu.hwcap_mask tunable is initialized already, so no need to do
- this. */
+#elif defined SHARED
+ /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86. The
+ glibc.cpu.hwcap_mask tunable is initialized already, so no
+ need to do this. */
GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
#endif
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index b2b90074b0..8a2ec92276 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -476,3 +476,449 @@ handle_zhaoxin (int name)
/* Nothing found. */
return 0;
}
+
+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
+dl_init_cacheinfo (struct cpu_features *cpu_features)
+{
+ /* 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;
+ unsigned long int level1_icache_size = -1;
+ unsigned long int level1_dcache_size = -1;
+ unsigned long int level1_dcache_assoc = -1;
+ unsigned long int level1_dcache_linesize = -1;
+ unsigned long int level2_cache_size = -1;
+ unsigned long int level2_cache_assoc = -1;
+ unsigned long int level2_cache_linesize = -1;
+ unsigned long int level3_cache_size = -1;
+ unsigned long int level3_cache_assoc = -1;
+ unsigned long int level3_cache_linesize = -1;
+ unsigned long int level4_cache_size = -1;
+
+ 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);
+
+ level1_icache_size
+ = handle_intel (_SC_LEVEL1_ICACHE_SIZE, cpu_features);
+ level1_dcache_size = data;
+ level1_dcache_assoc
+ = handle_intel (_SC_LEVEL1_DCACHE_ASSOC, cpu_features);
+ level1_dcache_linesize
+ = handle_intel (_SC_LEVEL1_DCACHE_LINESIZE, cpu_features);
+ level2_cache_size = core;
+ level2_cache_assoc
+ = handle_intel (_SC_LEVEL2_CACHE_ASSOC, cpu_features);
+ level2_cache_linesize
+ = handle_intel (_SC_LEVEL2_CACHE_LINESIZE, cpu_features);
+ level3_cache_size = shared;
+ level3_cache_assoc
+ = handle_intel (_SC_LEVEL3_CACHE_ASSOC, cpu_features);
+ level3_cache_linesize
+ = handle_intel (_SC_LEVEL3_CACHE_LINESIZE, cpu_features);
+ level4_cache_size
+ = handle_intel (_SC_LEVEL4_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);
+
+ level1_icache_size = handle_zhaoxin (_SC_LEVEL1_ICACHE_SIZE);
+ level1_dcache_size = data;
+ level1_dcache_assoc = handle_zhaoxin (_SC_LEVEL1_DCACHE_ASSOC);
+ level1_dcache_linesize = handle_zhaoxin (_SC_LEVEL1_DCACHE_LINESIZE);
+ level2_cache_size = core;
+ level2_cache_assoc = handle_zhaoxin (_SC_LEVEL2_CACHE_ASSOC);
+ level2_cache_linesize = handle_zhaoxin (_SC_LEVEL2_CACHE_LINESIZE);
+ level3_cache_size = shared;
+ 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);
+ }
+ 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);
+
+ level1_icache_size = handle_amd (_SC_LEVEL1_ICACHE_SIZE);
+ level1_dcache_size = data;
+ level1_dcache_assoc = handle_amd (_SC_LEVEL1_DCACHE_ASSOC);
+ level1_dcache_linesize = handle_amd (_SC_LEVEL1_DCACHE_LINESIZE);
+ level2_cache_size = core;
+ level2_cache_assoc = handle_amd (_SC_LEVEL2_CACHE_ASSOC);
+ level2_cache_linesize = handle_amd (_SC_LEVEL2_CACHE_LINESIZE);
+ level3_cache_size = shared;
+ level3_cache_assoc = handle_amd (_SC_LEVEL3_CACHE_ASSOC);
+ level3_cache_linesize = handle_amd (_SC_LEVEL3_CACHE_LINESIZE);
+
+ /* 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;
+ }
+ }
+
+ cpu_features->level1_icache_size = level1_icache_size;
+ cpu_features->level1_dcache_size = level1_dcache_size;
+ cpu_features->level1_dcache_assoc = level1_dcache_assoc;
+ cpu_features->level1_dcache_linesize = level1_dcache_linesize;
+ cpu_features->level2_cache_size = level2_cache_size;
+ cpu_features->level2_cache_assoc = level2_cache_assoc;
+ cpu_features->level2_cache_linesize = level2_cache_linesize;
+ cpu_features->level3_cache_size = level3_cache_size;
+ cpu_features->level3_cache_assoc = level3_cache_assoc;
+ 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;
+
+#if HAVE_TUNABLES
+ /* NB: The REP MOVSB threshold must be greater than VEC_SIZE * 8. */
+ unsigned int minimum_rep_movsb_threshold;
+#endif
+ /* 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);
+#if HAVE_TUNABLES
+ minimum_rep_movsb_threshold = 64 * 8;
+#endif
+ }
+ else if (CPU_FEATURE_PREFERRED_P (cpu_features,
+ AVX_Fast_Unaligned_Load))
+ {
+ rep_movsb_threshold = 2048 * (32 / 16);
+#if HAVE_TUNABLES
+ minimum_rep_movsb_threshold = 32 * 8;
+#endif
+ }
+ else
+ {
+ rep_movsb_threshold = 2048 * (16 / 16);
+#if HAVE_TUNABLES
+ minimum_rep_movsb_threshold = 16 * 8;
+#endif
+ }
+
+ /* The default threshold to use Enhanced REP STOSB. */
+ unsigned long int rep_stosb_threshold = 2048;
+
+#if HAVE_TUNABLES
+ long int tunable_size;
+
+ tunable_size = TUNABLE_GET (x86_data_cache_size, long int, NULL);
+ /* NB: Ignore the default value 0. */
+ if (tunable_size)
+ data = tunable_size;
+
+ tunable_size = TUNABLE_GET (x86_shared_cache_size, long int, NULL);
+ /* NB: Ignore the default value 0. */
+ if (tunable_size)
+ shared = tunable_size;
+
+ tunable_size = TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
+ /* NB: Ignore the default value 0. */
+ if (tunable_size)
+ non_temporal_threshold = tunable_size;
+
+ tunable_size = TUNABLE_GET (x86_rep_movsb_threshold, long int, NULL);
+ if (tunable_size > minimum_rep_movsb_threshold)
+ rep_movsb_threshold = tunable_size;
+
+ /* NB: The default value of the x86_rep_stosb_threshold tunable is the
+ same as the default value of __x86_rep_stosb_threshold and the
+ minimum value is fixed. */
+ rep_stosb_threshold = TUNABLE_GET (x86_rep_stosb_threshold,
+ long int, NULL);
+
+ TUNABLE_SET_WITH_BOUNDS (x86_data_cache_size, long int, data,
+ 0, (long int) -1);
+ TUNABLE_SET_WITH_BOUNDS (x86_shared_cache_size, long int, shared,
+ 0, (long int) -1);
+ TUNABLE_SET_WITH_BOUNDS (x86_non_temporal_threshold, long int,
+ non_temporal_threshold, 0, (long int) -1);
+ TUNABLE_SET_WITH_BOUNDS (x86_rep_movsb_threshold, long int,
+ rep_movsb_threshold,
+ minimum_rep_movsb_threshold, (long int) -1);
+ TUNABLE_SET_WITH_BOUNDS (x86_rep_stosb_threshold, long int,
+ rep_stosb_threshold, 1, (long int) -1);
+#endif
+
+ cpu_features->data_cache_size = data;
+ cpu_features->shared_cache_size = shared;
+ cpu_features->non_temporal_threshold = non_temporal_threshold;
+ cpu_features->rep_movsb_threshold = rep_movsb_threshold;
+ cpu_features->rep_stosb_threshold = rep_stosb_threshold;
+}
diff --git a/sysdeps/x86/include/cpu-features.h b/sysdeps/x86/include/cpu-features.h
index f62be0b9b3..3f3bd93320 100644
--- a/sysdeps/x86/include/cpu-features.h
+++ b/sysdeps/x86/include/cpu-features.h
@@ -153,6 +153,28 @@ struct cpu_features
unsigned long int rep_movsb_threshold;
/* Threshold to use "rep stosb". */
unsigned long int rep_stosb_threshold;
+ /* _SC_LEVEL1_ICACHE_SIZE. */
+ unsigned long int level1_icache_size;
+ /* _SC_LEVEL1_DCACHE_SIZE. */
+ unsigned long int level1_dcache_size;
+ /* _SC_LEVEL1_DCACHE_ASSOC. */
+ unsigned long int level1_dcache_assoc;
+ /* _SC_LEVEL1_DCACHE_LINESIZE. */
+ unsigned long int level1_dcache_linesize;
+ /* _SC_LEVEL2_CACHE_ASSOC. */
+ unsigned long int level2_cache_size;
+ /* _SC_LEVEL2_DCACHE_ASSOC. */
+ unsigned long int level2_cache_assoc;
+ /* _SC_LEVEL2_CACHE_LINESIZE. */
+ unsigned long int level2_cache_linesize;
+ /* /_SC_LEVEL3_CACHE_SIZE. */
+ unsigned long int level3_cache_size;
+ /* _SC_LEVEL3_CACHE_ASSOC. */
+ unsigned long int level3_cache_assoc;
+ /* _SC_LEVEL3_CACHE_LINESIZE. */
+ unsigned long int level3_cache_linesize;
+ /* /_SC_LEVEL4_CACHE_SIZE. */
+ unsigned long int level4_cache_size;
};
# if defined (_LIBC) && !IS_IN (nonlib)
--
2.26.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* V3 [PATCH 2/2] ld.so: Add --list-tunables to print tunable values
2020-10-17 1:02 V3 [PATCH 0/2] ld.so: Add --list-tunables to print tunable values H.J. Lu via Libc-alpha
2020-10-17 1:02 ` V3 [PATCH 1/2] x86: Move x86 processor cache info to cpu_features H.J. Lu via Libc-alpha
@ 2020-10-17 1:02 ` H.J. Lu via Libc-alpha
1 sibling, 0 replies; 3+ messages in thread
From: H.J. Lu via Libc-alpha @ 2020-10-17 1:02 UTC (permalink / raw)
To: libc-alpha; +Cc: Florian Weimer
Pass --list-tunables to ld.so to print tunables with min and max values.
---
NEWS | 2 ++
elf/Makefile | 8 ++++++++
elf/dl-main.h | 2 +-
elf/dl-tunables.c | 36 ++++++++++++++++++++++++++++++++++++
elf/dl-tunables.h | 2 ++
elf/dl-usage.c | 7 ++++++-
elf/rtld.c | 23 +++++++++++++++++++++++
manual/tunables.texi | 37 +++++++++++++++++++++++++++++++++++++
8 files changed, 115 insertions(+), 2 deletions(-)
diff --git a/NEWS b/NEWS
index 6eb577a669..fed8d87313 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,8 @@ Version 2.33
Major new features:
+* Pass --list-tunables to ld.so to print tunable values.
+
* The dynamic linker accepts the --argv0 argument and provides opportunity
to change argv[0] string.
diff --git a/elf/Makefile b/elf/Makefile
index f10cc59e7c..86b282a32b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -44,6 +44,10 @@ dl-routines += dl-tunables
tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
+ifeq (yesyes,$(build-shared)$(run-built-tests))
+tests-special += $(objpfx)list-tunables.out
+endif
+
# Make sure that the compiler does not insert any library calls in tunables
# code paths.
ifeq (yes,$(have-loop-to-function))
@@ -1812,3 +1816,7 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
'$(test-wrapper-env)' '$(run_program_env)' \
'$(rpath-link)' 'test-argv0' > $@; \
$(evaluate-test)
+
+$(objpfx)list-tunables.out: $(objpfx)ld.so
+ $(objpfx)ld.so --list-tunables > $@; \
+ $(evaluate-test)
diff --git a/elf/dl-main.h b/elf/dl-main.h
index b51256d3b4..f229867b8e 100644
--- a/elf/dl-main.h
+++ b/elf/dl-main.h
@@ -63,7 +63,7 @@ struct audit_list
enum rtld_mode
{
rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
- rtld_mode_help,
+ rtld_mode_list_tunables, rtld_mode_help,
};
/* Aggregated state information extracted from environment variables
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 2ba2844075..048601b704 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -398,6 +398,42 @@ __tunables_init (char **envp)
}
}
+void
+__tunables_print (void)
+{
+ for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
+ {
+ tunable_t *cur = &tunable_list[i];
+ _dl_printf ("%s: ", cur->name);
+ switch (cur->type.type_code)
+ {
+ case TUNABLE_TYPE_INT_32:
+ _dl_printf ("%d (min: %d, max: %d)\n",
+ (int) cur->val.numval,
+ (int) cur->type.min,
+ (int) cur->type.max);
+ break;
+ case TUNABLE_TYPE_UINT_64:
+ _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
+ (long int) cur->val.numval,
+ (long int) cur->type.min,
+ (long int) cur->type.max);
+ break;
+ case TUNABLE_TYPE_SIZE_T:
+ _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
+ (size_t) cur->val.numval,
+ (size_t) cur->type.min,
+ (size_t) cur->type.max);
+ break;
+ case TUNABLE_TYPE_STRING:
+ _dl_printf ("%s\n", cur->val.strval ? cur->val.strval : "");
+ break;
+ default:
+ __builtin_unreachable ();
+ }
+ }
+}
+
/* Set the tunable value. This is called by the module that the tunable exists
in. */
void
diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
index 550b0cc7f4..4a0c90f3e0 100644
--- a/elf/dl-tunables.h
+++ b/elf/dl-tunables.h
@@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
# include "dl-tunable-list.h"
extern void __tunables_init (char **);
+extern void __tunables_print (void);
extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
rtld_hidden_proto (__tunables_init)
+rtld_hidden_proto (__tunables_print)
rtld_hidden_proto (__tunable_get_val)
rtld_hidden_proto (__tunable_set_val)
diff --git a/elf/dl-usage.c b/elf/dl-usage.c
index 796ad38b43..3ce19fb892 100644
--- a/elf/dl-usage.c
+++ b/elf/dl-usage.c
@@ -190,7 +190,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
in LIST\n\
--audit LIST use objects named in LIST as auditors\n\
--preload LIST preload objects named in LIST\n\
- --argv0 STRING set argv[0] to STRING before running\n\
+ --argv0 STRING set argv[0] to STRING before running\n"
+#if HAVE_TUNABLES
+"\
+ --list-tunables list all tunables with minimum and maximum values\n"
+#endif
+"\
--help display this help and exit\n\
--version output version information and exit\n\
\n\
diff --git a/elf/rtld.c b/elf/rtld.c
index 5d117d0d2c..33993a6f8b 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -49,6 +49,10 @@
#include <libc-early-init.h>
#include <dl-main.h>
+#if HAVE_TUNABLES
+# include <dl-tunables.h>
+#endif
+
#include <assert.h>
/* Only enables rtld profiling for architectures which provides non generic
@@ -1248,6 +1252,16 @@ dl_main (const ElfW(Phdr) *phdr,
_dl_argc -= 2;
_dl_argv += 2;
}
+#if HAVE_TUNABLES
+ else if (! strcmp (_dl_argv[1], "--list-tunables"))
+ {
+ state.mode = rtld_mode_list_tunables;
+
+ ++_dl_skip_args;
+ --_dl_argc;
+ ++_dl_argv;
+ }
+#endif
else if (strcmp (_dl_argv[1], "--help") == 0)
{
state.mode = rtld_mode_help;
@@ -1268,6 +1282,15 @@ dl_main (const ElfW(Phdr) *phdr,
else
break;
+#if HAVE_TUNABLES
+ if (__builtin_expect (state.mode, rtld_mode_normal)
+ == rtld_mode_list_tunables)
+ {
+ __tunables_print ();
+ _exit (0);
+ }
+#endif
+
/* If we have no further argument the program was called incorrectly.
Grant the user some education. */
if (_dl_argc < 2)
diff --git a/manual/tunables.texi b/manual/tunables.texi
index d72d7a5ec0..924dac8876 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -28,6 +28,43 @@ Finally, the set of tunables available may vary between distributions as
the tunables feature allows distributions to add their own tunables under
their own namespace.
+Passing @option{--list-tunables} to the dynamic loader to print all
+tunables with minimum and maximum values:
+
+@example
+$ /lib64/ld-linux-x86-64.so.2 --list-tunables
+glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
+glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.perturb: 0 (min: 0, max: 255)
+glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
+glibc.elision.enable: 0 (min: 0, max: 1)
+glibc.cpu.x86_rep_movsb_threshold: 0x800 (min: 0x100, max: 0xffffffffffffffff)
+glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
+glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_shstk:
+glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
+glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_ibt:
+glibc.cpu.hwcaps:
+glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
+glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
+glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
+glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.malloc.check: 0 (min: 0, max: 3)
+@end example
+
@menu
* Tunable names:: The structure of a tunable name
* Memory Allocation Tunables:: Tunables in the memory allocation subsystem
--
2.26.2
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