1#define JEMALLOC_PAGES_C_
2#include "jemalloc/internal/jemalloc_internal.h"
3
4#ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
5#include <sys/sysctl.h>
6#endif
7
8/******************************************************************************/
9/* Data. */
10
11#ifndef _WIN32
12# define PAGES_PROT_COMMIT (PROT_READ | PROT_WRITE)
13# define PAGES_PROT_DECOMMIT (PROT_NONE)
14static int mmap_flags;
15#endif
16static bool os_overcommits;
17
18/******************************************************************************/
19
20void *
21pages_map(void *addr, size_t size, bool *commit)
22{
23 void *ret;
24
25 assert(size != 0);
26
27 if (os_overcommits)
28 *commit = true;
29
30#ifdef _WIN32
31 /*
32 * If VirtualAlloc can't allocate at the given address when one is
33 * given, it fails and returns NULL.
34 */
35 ret = VirtualAlloc(addr, size, MEM_RESERVE | (*commit ? MEM_COMMIT : 0),
36 PAGE_READWRITE);
37#else
38 /*
39 * We don't use MAP_FIXED here, because it can cause the *replacement*
40 * of existing mappings, and we only want to create new mappings.
41 */
42 {
43 int prot = *commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
44
45 ret = mmap(addr, size, prot, mmap_flags, -1, 0);
46 }
47 assert(ret != NULL);
48
49 if (ret == MAP_FAILED)
50 ret = NULL;
51 else if (addr != NULL && ret != addr) {
52 /*
53 * We succeeded in mapping memory, but not in the right place.
54 */
55 pages_unmap(ret, size);
56 ret = NULL;
57 }
58#endif
59 assert(ret == NULL || (addr == NULL && ret != addr)
60 || (addr != NULL && ret == addr));
61 return (ret);
62}
63
64void
65pages_unmap(void *addr, size_t size)
66{
67
68#ifdef _WIN32
69 if (VirtualFree(addr, 0, MEM_RELEASE) == 0)
70#else
71 if (munmap(addr, size) == -1)
72#endif
73 {
74 char buf[BUFERROR_BUF];
75
76 buferror(get_errno(), buf, sizeof(buf));
77 malloc_printf("<jemalloc>: Error in "
78#ifdef _WIN32
79 "VirtualFree"
80#else
81 "munmap"
82#endif
83 "(): %s\n", buf);
84 if (opt_abort)
85 abort();
86 }
87}
88
89void *
90pages_trim(void *addr, size_t alloc_size, size_t leadsize, size_t size,
91 bool *commit)
92{
93 void *ret = (void *)((uintptr_t)addr + leadsize);
94
95 assert(alloc_size >= leadsize + size);
96#ifdef _WIN32
97 {
98 void *new_addr;
99
100 pages_unmap(addr, alloc_size);
101 new_addr = pages_map(ret, size, commit);
102 if (new_addr == ret)
103 return (ret);
104 if (new_addr)
105 pages_unmap(new_addr, size);
106 return (NULL);
107 }
108#else
109 {
110 size_t trailsize = alloc_size - leadsize - size;
111
112 if (leadsize != 0)
113 pages_unmap(addr, leadsize);
114 if (trailsize != 0)
115 pages_unmap((void *)((uintptr_t)ret + size), trailsize);
116 return (ret);
117 }
118#endif
119}
120
121static bool
122pages_commit_impl(void *addr, size_t size, bool commit)
123{
124
125 if (os_overcommits)
126 return (true);
127
128#ifdef _WIN32
129 return (commit ? (addr != VirtualAlloc(addr, size, MEM_COMMIT,
130 PAGE_READWRITE)) : (!VirtualFree(addr, size, MEM_DECOMMIT)));
131#else
132 {
133 int prot = commit ? PAGES_PROT_COMMIT : PAGES_PROT_DECOMMIT;
134 void *result = mmap(addr, size, prot, mmap_flags | MAP_FIXED,
135 -1, 0);
136 if (result == MAP_FAILED)
137 return (true);
138 if (result != addr) {
139 /*
140 * We succeeded in mapping memory, but not in the right
141 * place.
142 */
143 pages_unmap(result, size);
144 return (true);
145 }
146 return (false);
147 }
148#endif
149}
150
151bool
152pages_commit(void *addr, size_t size)
153{
154
155 return (pages_commit_impl(addr, size, true));
156}
157
158bool
159pages_decommit(void *addr, size_t size)
160{
161
162 return (pages_commit_impl(addr, size, false));
163}
164
165bool
166pages_purge(void *addr, size_t size)
167{
168 bool unzeroed;
169
170#ifdef _WIN32
171 VirtualAlloc(addr, size, MEM_RESET, PAGE_READWRITE);
172 unzeroed = true;
173#elif defined(JEMALLOC_HAVE_MADVISE)
174# ifdef JEMALLOC_PURGE_MADVISE_DONTNEED
175# define JEMALLOC_MADV_PURGE MADV_DONTNEED
176# define JEMALLOC_MADV_ZEROS true
177# elif defined(JEMALLOC_PURGE_MADVISE_FREE)
178# define JEMALLOC_MADV_PURGE MADV_FREE
179# define JEMALLOC_MADV_ZEROS false
180# else
181# error "No madvise(2) flag defined for purging unused dirty pages."
182# endif
183 int err = madvise(addr, size, JEMALLOC_MADV_PURGE);
184 unzeroed = (!JEMALLOC_MADV_ZEROS || err != 0);
185# undef JEMALLOC_MADV_PURGE
186# undef JEMALLOC_MADV_ZEROS
187#else
188 /* Last resort no-op. */
189 unzeroed = true;
190#endif
191 return (unzeroed);
192}
193
194#ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
195static bool
196os_overcommits_sysctl(void)
197{
198 int vm_overcommit;
199 size_t sz;
200
201 sz = sizeof(vm_overcommit);
202 if (sysctlbyname("vm.overcommit", &vm_overcommit, &sz, NULL, 0) != 0)
203 return (false); /* Error. */
204
205 return ((vm_overcommit & 0x3) == 0);
206}
207#endif
208
209#ifdef JEMALLOC_PROC_SYS_VM_OVERCOMMIT_MEMORY
210static bool
211os_overcommits_proc(void)
212{
213 int fd;
214 char buf[1];
215 ssize_t nread;
216
217 fd = open("/proc/sys/vm/overcommit_memory", O_RDONLY);
218 if (fd == -1)
219 return (false); /* Error. */
220
221 nread = read(fd, &buf, sizeof(buf));
222 if (nread < 1)
223 return (false); /* Error. */
224 /*
225 * /proc/sys/vm/overcommit_memory meanings:
226 * 0: Heuristic overcommit.
227 * 1: Always overcommit.
228 * 2: Never overcommit.
229 */
230 return (buf[0] == '0' || buf[0] == '1');
231}
232#endif
233
234void
235pages_boot(void)
236{
237
238#ifndef _WIN32
239 mmap_flags = MAP_PRIVATE | MAP_ANON;
240#endif
241
242#ifdef JEMALLOC_SYSCTL_VM_OVERCOMMIT
243 os_overcommits = os_overcommits_sysctl();
244#elif defined(JEMALLOC_PROC_SYS_VM_OVERCOMMIT_MEMORY)
245 os_overcommits = os_overcommits_proc();
246# ifdef MAP_NORESERVE
247 if (os_overcommits)
248 mmap_flags |= MAP_NORESERVE;
249# endif
250#else
251 os_overcommits = false;
252#endif
253}
254