1/* x86 cache info.
2 Copyright (C) 2020-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <unistd.h>
21#include <cpuid.h>
22#include <cpu-features.h>
23
24#define TUNABLE_NAMESPACE cpu
25#include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
26#include <elf/dl-tunables.h>
27
28#if IS_IN (libc)
29/* Data cache size for use in memory and string routines, typically
30 L1 size, rounded to multiple of 256 bytes. */
31long int __x86_data_cache_size_half attribute_hidden = 32 * 1024 / 2;
32long int __x86_data_cache_size attribute_hidden = 32 * 1024;
33/* Shared cache size for use in memory and string routines, typically
34 L2 or L3 size, rounded to multiple of 256 bytes. */
35long int __x86_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2;
36long int __x86_shared_cache_size attribute_hidden = 1024 * 1024;
37
38/* Threshold to use non temporal store. */
39long int __x86_shared_non_temporal_threshold attribute_hidden;
40
41/* Threshold to use Enhanced REP MOVSB. */
42long int __x86_rep_movsb_threshold attribute_hidden = 2048;
43
44/* Threshold to use Enhanced REP STOSB. */
45long int __x86_rep_stosb_threshold attribute_hidden = 2048;
46
47/* Threshold to stop using Enhanced REP MOVSB. */
48long int __x86_rep_movsb_stop_threshold attribute_hidden;
49
50/* A bit-wise OR of string/memory requirements for optimal performance
51 e.g. X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB. These bits
52 are used at runtime to tune implementation behavior. */
53int __x86_string_control attribute_hidden;
54
55static void
56init_cacheinfo (void)
57{
58 const struct cpu_features *cpu_features = __get_cpu_features ();
59 long int data = cpu_features->data_cache_size;
60 /* Round data cache size to multiple of 256 bytes. */
61 data = data & ~255L;
62 if (data > 0)
63 {
64 __x86_data_cache_size_half = data / 2;
65 __x86_data_cache_size = data;
66 }
67
68 long int shared = cpu_features->shared_cache_size;
69 /* Round shared cache size to multiple of 256 bytes. */
70 shared = shared & ~255L;
71 if (shared > 0)
72 {
73 __x86_shared_cache_size_half = shared / 2;
74 __x86_shared_cache_size = shared;
75 }
76
77 __x86_shared_non_temporal_threshold
78 = cpu_features->non_temporal_threshold;
79
80 __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
81 __x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
82 __x86_rep_movsb_stop_threshold = cpu_features->rep_movsb_stop_threshold;
83
84 if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_Short_Distance_REP_MOVSB))
85 __x86_string_control
86 |= X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB;
87}
88#endif
89