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