1 #ifndef JEMALLOC_INTERNAL_CACHE_BIN_H 2 #define JEMALLOC_INTERNAL_CACHE_BIN_H 3 4 #include "jemalloc/internal/ql.h" 5 6 /* 7 * The cache_bins are the mechanism that the tcache and the arena use to 8 * communicate. The tcache fills from and flushes to the arena by passing a 9 * cache_bin_t to fill/flush. When the arena needs to pull stats from the 10 * tcaches associated with it, it does so by iterating over its 11 * cache_bin_array_descriptor_t objects and reading out per-bin stats it 12 * contains. This makes it so that the arena need not know about the existence 13 * of the tcache at all. 14 */ 15 16 17 /* 18 * The count of the number of cached allocations in a bin. We make this signed 19 * so that negative numbers can encode "invalid" states (e.g. a low water mark 20 * of -1 for a cache that has been depleted). 21 */ 22 typedef int32_t cache_bin_sz_t; 23 24 typedef struct cache_bin_stats_s cache_bin_stats_t; 25 struct cache_bin_stats_s { 26 /* 27 * Number of allocation requests that corresponded to the size of this 28 * bin. 29 */ 30 uint64_t nrequests; 31 }; 32 33 /* 34 * Read-only information associated with each element of tcache_t's tbins array 35 * is stored separately, mainly to reduce memory usage. 36 */ 37 typedef struct cache_bin_info_s cache_bin_info_t; 38 struct cache_bin_info_s { 39 /* Upper limit on ncached. */ 40 cache_bin_sz_t ncached_max; 41 }; 42 43 typedef struct cache_bin_s cache_bin_t; 44 struct cache_bin_s { 45 /* Min # cached since last GC. */ 46 cache_bin_sz_t low_water; 47 /* # of cached objects. */ 48 cache_bin_sz_t ncached; 49 /* Removing this variable make the cache_t structure fit in a single page. */ 50 #if defined(ANDROID_ENABLE_TCACHE_STATS) 51 /* 52 * ncached and stats are both modified frequently. Let's keep them 53 * close so that they have a higher chance of being on the same 54 * cacheline, thus less write-backs. 55 */ 56 cache_bin_stats_t tstats; 57 #endif 58 /* 59 * Stack of available objects. 60 * 61 * To make use of adjacent cacheline prefetch, the items in the avail 62 * stack goes to higher address for newer allocations. avail points 63 * just above the available space, which means that 64 * avail[-ncached, ... -1] are available items and the lowest item will 65 * be allocated first. 66 */ 67 void **avail; 68 }; 69 70 typedef struct cache_bin_array_descriptor_s cache_bin_array_descriptor_t; 71 struct cache_bin_array_descriptor_s { 72 /* 73 * The arena keeps a list of the cache bins associated with it, for 74 * stats collection. 75 */ 76 ql_elm(cache_bin_array_descriptor_t) link; 77 /* Pointers to the tcache bins. */ 78 cache_bin_t *bins_small; 79 cache_bin_t *bins_large; 80 }; 81 82 static inline void 83 cache_bin_array_descriptor_init(cache_bin_array_descriptor_t *descriptor, 84 cache_bin_t *bins_small, cache_bin_t *bins_large) { 85 ql_elm_new(descriptor, link); 86 descriptor->bins_small = bins_small; 87 descriptor->bins_large = bins_large; 88 } 89 90 JEMALLOC_ALWAYS_INLINE void * 91 cache_bin_alloc_easy(cache_bin_t *bin, bool *success) { 92 void *ret; 93 94 if (unlikely(bin->ncached == 0)) { 95 bin->low_water = -1; 96 *success = false; 97 return NULL; 98 } 99 /* 100 * success (instead of ret) should be checked upon the return of this 101 * function. We avoid checking (ret == NULL) because there is never a 102 * null stored on the avail stack (which is unknown to the compiler), 103 * and eagerly checking ret would cause pipeline stall (waiting for the 104 * cacheline). 105 */ 106 *success = true; 107 ret = *(bin->avail - bin->ncached); 108 bin->ncached--; 109 110 if (unlikely(bin->ncached < bin->low_water)) { 111 bin->low_water = bin->ncached; 112 } 113 114 return ret; 115 } 116 117 #endif /* JEMALLOC_INTERNAL_CACHE_BIN_H */ 118
