cache.h (2616B)
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 */