1 #define JEMALLOC_CHUNK_MMAP_C_ 2 #include "jemalloc/internal/jemalloc_internal.h" 3 4 /******************************************************************************/ 5 6 static void * 7 chunk_alloc_mmap_slow(size_t size, size_t alignment, bool *zero, bool *commit) 8 { 9 void *ret; 10 size_t alloc_size; 11 12 alloc_size = size + alignment - PAGE; 13 /* Beware size_t wrap-around. */ 14 if (alloc_size < size) 15 return (NULL); 16 do { 17 void *pages; 18 size_t leadsize; 19 pages = pages_map(NULL, alloc_size); 20 if (pages == NULL) 21 return (NULL); 22 leadsize = ALIGNMENT_CEILING((uintptr_t)pages, alignment) - 23 (uintptr_t)pages; 24 ret = pages_trim(pages, alloc_size, leadsize, size); 25 } while (ret == NULL); 26 27 assert(ret != NULL); 28 *zero = true; 29 if (!*commit) 30 *commit = pages_decommit(ret, size); 31 return (ret); 32 } 33 34 void * 35 chunk_alloc_mmap(void *new_addr, size_t size, size_t alignment, bool *zero, 36 bool *commit) 37 { 38 void *ret; 39 size_t offset; 40 41 /* 42 * Ideally, there would be a way to specify alignment to mmap() (like 43 * NetBSD has), but in the absence of such a feature, we have to work 44 * hard to efficiently create aligned mappings. The reliable, but 45 * slow method is to create a mapping that is over-sized, then trim the 46 * excess. However, that always results in one or two calls to 47 * pages_unmap(). 48 * 49 * Optimistically try mapping precisely the right amount before falling 50 * back to the slow method, with the expectation that the optimistic 51 * approach works most of the time. 52 */ 53 54 assert(alignment != 0); 55 assert((alignment & chunksize_mask) == 0); 56 57 ret = pages_map(new_addr, size); 58 if (ret == NULL || ret == new_addr) 59 return (ret); 60 assert(new_addr == NULL); 61 offset = ALIGNMENT_ADDR2OFFSET(ret, alignment); 62 if (offset != 0) { 63 pages_unmap(ret, size); 64 return (chunk_alloc_mmap_slow(size, alignment, zero, commit)); 65 } 66 67 assert(ret != NULL); 68 *zero = true; 69 if (!*commit) 70 *commit = pages_decommit(ret, size); 71 return (ret); 72 } 73 74 bool 75 chunk_dalloc_mmap(void *chunk, size_t size) 76 { 77 78 if (config_munmap) 79 pages_unmap(chunk, size); 80 81 return (!config_munmap); 82 } 83
