1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_CACHE_H
3#define __LINUX_CACHE_H
4
5#include <uapi/linux/kernel.h>
6#include <asm/cache.h>
7
8#ifndef L1_CACHE_ALIGN
9#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
10#endif
11
12#ifndef SMP_CACHE_BYTES
13#define SMP_CACHE_BYTES L1_CACHE_BYTES
14#endif
15
16/*
17 * __read_mostly is used to keep rarely changing variables out of frequently
18 * updated cachelines. Its use should be reserved for data that is used
19 * frequently in hot paths. Performance traces can help decide when to use
20 * this. You want __read_mostly data to be tightly packed, so that in the
21 * best case multiple frequently read variables for a hot path will be next
22 * to each other in order to reduce the number of cachelines needed to
23 * execute a critical path. We should be mindful and selective of its use.
24 * ie: if you're going to use it please supply a *good* justification in your
25 * commit log
26 */
27#ifndef __read_mostly
28#define __read_mostly
29#endif
30
31/*
32 * __ro_after_init is used to mark things that are read-only after init (i.e.
33 * after mark_rodata_ro() has been called). These are effectively read-only,
34 * but may get written to during init, so can't live in .rodata (via "const").
35 */
36#ifndef __ro_after_init
37#define __ro_after_init __section(".data..ro_after_init")
38#endif
39
40#ifndef ____cacheline_aligned
41#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
42#endif
43
44#ifndef ____cacheline_aligned_in_smp
45#ifdef CONFIG_SMP
46#define ____cacheline_aligned_in_smp ____cacheline_aligned
47#else
48#define ____cacheline_aligned_in_smp
49#endif /* CONFIG_SMP */
50#endif
51
52#ifndef __cacheline_aligned
53#define __cacheline_aligned \
54 __attribute__((__aligned__(SMP_CACHE_BYTES), \
55 __section__(".data..cacheline_aligned")))
56#endif /* __cacheline_aligned */
57
58#ifndef __cacheline_aligned_in_smp
59#ifdef CONFIG_SMP
60#define __cacheline_aligned_in_smp __cacheline_aligned
61#else
62#define __cacheline_aligned_in_smp
63#endif /* CONFIG_SMP */
64#endif
65
66/*
67 * The maximum alignment needed for some critical structures
68 * These could be inter-node cacheline sizes/L3 cacheline
69 * size etc. Define this in asm/cache.h for your arch
70 */
71#ifndef INTERNODE_CACHE_SHIFT
72#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
73#endif
74
75#if !defined(____cacheline_internodealigned_in_smp)
76#if defined(CONFIG_SMP)
77#define ____cacheline_internodealigned_in_smp \
78 __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
79#else
80#define ____cacheline_internodealigned_in_smp
81#endif
82#endif
83
84#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
85#define cache_line_size() L1_CACHE_BYTES
86#endif
87
88#endif /* __LINUX_CACHE_H */
89

source code of linux/include/linux/cache.h