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Diffstat (limited to 'include/linux/cache.h')
-rw-r--r-- | include/linux/cache.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/include/linux/cache.h b/include/linux/cache.h new file mode 100644 index 000000000..5da1bbd96 --- /dev/null +++ b/include/linux/cache.h @@ -0,0 +1,101 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __LINUX_CACHE_H +#define __LINUX_CACHE_H + +#include <uapi/linux/kernel.h> +#include <asm/cache.h> + +#ifndef L1_CACHE_ALIGN +#define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES) +#endif + +#ifndef SMP_CACHE_BYTES +#define SMP_CACHE_BYTES L1_CACHE_BYTES +#endif + +/* + * __read_mostly is used to keep rarely changing variables out of frequently + * updated cachelines. Its use should be reserved for data that is used + * frequently in hot paths. Performance traces can help decide when to use + * this. You want __read_mostly data to be tightly packed, so that in the + * best case multiple frequently read variables for a hot path will be next + * to each other in order to reduce the number of cachelines needed to + * execute a critical path. We should be mindful and selective of its use. + * ie: if you're going to use it please supply a *good* justification in your + * commit log + */ +#ifndef __read_mostly +#define __read_mostly +#endif + +/* + * __ro_after_init is used to mark things that are read-only after init (i.e. + * after mark_rodata_ro() has been called). These are effectively read-only, + * but may get written to during init, so can't live in .rodata (via "const"). + */ +#ifndef __ro_after_init +#define __ro_after_init __section(".data..ro_after_init") +#endif + +#ifndef ____cacheline_aligned +#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES))) +#endif + +#ifndef ____cacheline_aligned_in_smp +#ifdef CONFIG_SMP +#define ____cacheline_aligned_in_smp ____cacheline_aligned +#else +#define ____cacheline_aligned_in_smp +#endif /* CONFIG_SMP */ +#endif + +#ifndef __cacheline_aligned +#define __cacheline_aligned \ + __attribute__((__aligned__(SMP_CACHE_BYTES), \ + __section__(".data..cacheline_aligned"))) +#endif /* __cacheline_aligned */ + +#ifndef __cacheline_aligned_in_smp +#ifdef CONFIG_SMP +#define __cacheline_aligned_in_smp __cacheline_aligned +#else +#define __cacheline_aligned_in_smp +#endif /* CONFIG_SMP */ +#endif + +/* + * The maximum alignment needed for some critical structures + * These could be inter-node cacheline sizes/L3 cacheline + * size etc. Define this in asm/cache.h for your arch + */ +#ifndef INTERNODE_CACHE_SHIFT +#define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT +#endif + +#if !defined(____cacheline_internodealigned_in_smp) +#if defined(CONFIG_SMP) +#define ____cacheline_internodealigned_in_smp \ + __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT)))) +#else +#define ____cacheline_internodealigned_in_smp +#endif +#endif + +#ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE +#define cache_line_size() L1_CACHE_BYTES +#endif + +/* + * Helper to add padding within a struct to ensure data fall into separate + * cachelines. + */ +#if defined(CONFIG_SMP) +struct cacheline_padding { + char x[0]; +} ____cacheline_internodealigned_in_smp; +#define CACHELINE_PADDING(name) struct cacheline_padding name +#else +#define CACHELINE_PADDING(name) +#endif + +#endif /* __LINUX_CACHE_H */ |