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