| 1 |
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| 2 | #ifndef __LINUX_CACHE_H
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| 3 | #define __LINUX_CACHE_H
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| 4 |
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| 5 | #include <uapi/linux/kernel.h>
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| 6 | #include <asm/cache.h>
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| 7 |
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| 8 | #ifndef L1_CACHE_ALIGN
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| 9 | #define L1_CACHE_ALIGN(x) __ALIGN_KERNEL(x, L1_CACHE_BYTES)
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| 10 | #endif
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| 11 |
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| 12 | #ifndef SMP_CACHE_BYTES
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| 13 | #define SMP_CACHE_BYTES L1_CACHE_BYTES
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| 14 | #endif
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| 15 |
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| 16 | |
| 17 | * __read_mostly is used to keep rarely changing variables out of frequently
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| 18 | * updated cachelines. Its use should be reserved for data that is used
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| 19 | * frequently in hot paths. Performance traces can help decide when to use
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| 20 | * this. You want __read_mostly data to be tightly packed, so that in the
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| 21 | * best case multiple frequently read variables for a hot path will be next
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| 22 | * to each other in order to reduce the number of cachelines needed to
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| 23 | * execute a critical path. We should be mindful and selective of its use.
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| 24 | * ie: if you're going to use it please supply a *good* justification in your
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| 25 | * commit log
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| 26 |
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| 27 | #ifndef __read_mostly
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| 28 | #define __read_mostly
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| 29 | #endif
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| 30 |
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| 31 | |
| 32 | * __ro_after_init is used to mark things that are read-only after init (i.e.
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| 33 | * after mark_rodata_ro() has been called). These are effectively read-only,
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| 34 | * but may get written to during init, so can't live in .rodata (via "const").
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| 35 |
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| 36 | #ifndef __ro_after_init
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| 37 | #define __ro_after_init __section(".data..ro_after_init")
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| 38 | #endif
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| 39 |
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| 40 | #ifndef ____cacheline_aligned
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| 41 | #define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
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| 42 | #endif
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| 43 |
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| 44 | #ifndef ____cacheline_aligned_in_smp
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| 45 | #ifdef CONFIG_SMP
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| 46 | #define ____cacheline_aligned_in_smp ____cacheline_aligned
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| 47 | #else
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| 48 | #define ____cacheline_aligned_in_smp
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| 49 | #endif
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| 50 | #endif
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| 51 |
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| 52 | #ifndef __cacheline_aligned
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| 53 | #define __cacheline_aligned \
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| 54 | __attribute__((__aligned__(SMP_CACHE_BYTES), \
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| 55 | __section__(".data..cacheline_aligned")))
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| 56 | #endif
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| 57 |
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| 58 | #ifndef __cacheline_aligned_in_smp
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| 59 | #ifdef CONFIG_SMP
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| 60 | #define __cacheline_aligned_in_smp __cacheline_aligned
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| 61 | #else
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| 62 | #define __cacheline_aligned_in_smp
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| 63 | #endif
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| 64 | #endif
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| 65 |
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| 66 | |
| 67 | * The maximum alignment needed for some critical structures
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| 68 | * These could be inter-node cacheline sizes/L3 cacheline
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| 69 | * size etc. Define this in asm/cache.h for your arch
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| 70 |
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| 71 | #ifndef INTERNODE_CACHE_SHIFT
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| 72 | #define INTERNODE_CACHE_SHIFT L1_CACHE_SHIFT
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| 73 | #endif
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| 74 |
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| 75 | #if !defined(____cacheline_internodealigned_in_smp)
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| 76 | #if defined(CONFIG_SMP)
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| 77 | #define ____cacheline_internodealigned_in_smp \
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| 78 | __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
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| 79 | #else
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| 80 | #define ____cacheline_internodealigned_in_smp
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| 81 | #endif
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| 82 | #endif
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| 83 |
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| 84 | #ifndef CONFIG_ARCH_HAS_CACHE_LINE_SIZE
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| 85 | #define cache_line_size() L1_CACHE_BYTES
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| 86 | #endif
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| 87 |
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| 88 | |
| 89 | * Helper to add padding within a struct to ensure data fall into separate
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| 90 | * cachelines.
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| 91 |
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| 92 | #if defined(CONFIG_SMP)
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| 93 | struct cacheline_padding {
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| 94 | char x[0];
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| 95 | } ____cacheline_internodealigned_in_smp;
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| 96 | #define CACHELINE_PADDING(name) struct cacheline_padding name
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| 97 | #else
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| 98 | #define CACHELINE_PADDING(name)
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| 99 | #endif
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| 100 |
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| 101 | #endif
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