1/* x86 cache info.
2 Copyright (C) 2020-2022 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#if HAVE_TUNABLES
25# define TUNABLE_NAMESPACE cpu
26# include <unistd.h> /* Get STDOUT_FILENO for _dl_printf. */
27# include <elf/dl-tunables.h>
28#endif
29
30#if IS_IN (libc)
31/* Data cache size for use in memory and string routines, typically
32 L1 size, rounded to multiple of 256 bytes. */
33long int __x86_data_cache_size_half attribute_hidden = 32 * 1024 / 2;
34long int __x86_data_cache_size attribute_hidden = 32 * 1024;
35/* Shared cache size for use in memory and string routines, typically
36 L2 or L3 size, rounded to multiple of 256 bytes. */
37long int __x86_shared_cache_size_half attribute_hidden = 1024 * 1024 / 2;
38long int __x86_shared_cache_size attribute_hidden = 1024 * 1024;
39
40/* Threshold to use non temporal store. */
41long int __x86_shared_non_temporal_threshold attribute_hidden;
42
43/* Threshold to use Enhanced REP MOVSB. */
44long int __x86_rep_movsb_threshold attribute_hidden = 2048;
45
46/* Threshold to use Enhanced REP STOSB. */
47long int __x86_rep_stosb_threshold attribute_hidden = 2048;
48
49/* Threshold to stop using Enhanced REP MOVSB. */
50long int __x86_rep_movsb_stop_threshold attribute_hidden;
51
52/* A bit-wise OR of string/memory requirements for optimal performance
53 e.g. X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB. These bits
54 are used at runtime to tune implementation behavior. */
55int __x86_string_control attribute_hidden;
56
57static void
58init_cacheinfo (void)
59{
60 const struct cpu_features *cpu_features = __get_cpu_features ();
61 long int data = cpu_features->data_cache_size;
62 /* Round data cache size to multiple of 256 bytes. */
63 data = data & ~255L;
64 if (data > 0)
65 {
66 __x86_data_cache_size_half = data / 2;
67 __x86_data_cache_size = data;
68 }
69
70 long int shared = cpu_features->shared_cache_size;
71 /* Round shared cache size to multiple of 256 bytes. */
72 shared = shared & ~255L;
73 if (shared > 0)
74 {
75 __x86_shared_cache_size_half = shared / 2;
76 __x86_shared_cache_size = shared;
77 }
78
79 __x86_shared_non_temporal_threshold
80 = cpu_features->non_temporal_threshold;
81
82 __x86_rep_movsb_threshold = cpu_features->rep_movsb_threshold;
83 __x86_rep_stosb_threshold = cpu_features->rep_stosb_threshold;
84 __x86_rep_movsb_stop_threshold = cpu_features->rep_movsb_stop_threshold;
85
86 if (CPU_FEATURES_ARCH_P (cpu_features, Avoid_Short_Distance_REP_MOVSB))
87 __x86_string_control
88 |= X86_STRING_CONTROL_AVOID_SHORT_DISTANCE_REP_MOVSB;
89}
90#endif
91