| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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 |
| Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame] | 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 |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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 |
| Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame] | 37 | #define __ro_after_init __section(".data..ro_after_init") |
| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame] | 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 */ |