1MALLOC_INFO(3) Linux Programmer's Manual MALLOC_INFO(3)
2
6 malloc_info - export malloc state to a stream
7
9 #include <malloc.h>
10 int malloc_info(int options, FILE *fp);
12
14 The malloc_info() function exports an XML string that describes the
15 current state of the memory-allocation implementation in the caller.
16 The string is printed on the file stream fp. The exported string
17 includes information about all arenas (see malloc(3)).
18 As currently implemented, options must be zero.
20
22 On success, malloc_info() returns 0; on error, it returns -1, with
23 errno set to indicate the cause.
24
26 EINVAL options was nonzero.
27
29 malloc_info() was added to glibc in version 2.10.
30
32 This function is a GNU extension.
33
35 The memory-allocation information is provided as an XML string (rather
36 than a C structure) because the information may change over time
37 (according to changes in the underlying implementation). The output
38 XML string includes a version field.
39 The open_memstream(3) function can be used to send the output of mal‐
41 loc_info() directly into a buffer in memory, rather than to a file.
42 The malloc_info() function is designed to address deficiencies in mal‐
44 loc_stats(3) and mallinfo(3).
45
47 The program below takes up to four command-line arguments, of which the
48 first three are mandatory. The first argument specifies the number of
49 threads that the program should create. All of the threads, including
50 the main thread, allocate the number of blocks of memory specified by
51 the second argument. The third argument controls the size of the
52 blocks to be allocated. The main thread creates blocks of this size,
53 the second thread created by the program allocates blocks of twice this
54 size, the third thread allocates blocks of three times this size, and
55 so on.
56 The program calls malloc_info() twice to display the memory-allocation
58 state. The first call takes place before any threads are created or
59 memory allocated. The second call is performed after all threads have
60 allocated memory.
61 In the following example, the command-line arguments specify the cre‐
63 ation of one additional thread, and both the main thread and the addi‐
64 tional thread allocate 10000 blocks of memory. After the blocks of
65 memory have been allocated, malloc_info() shows the state of two allo‐
66 cation arenas.
67 $ getconf GNU_LIBC_VERSION
69 glibc 2.13
70 $ ./a.out 1 10000 100
71 ============ Before allocating blocks ============
72 <malloc version="1">
73 <heap nr="0">
74 <sizes>
75 </sizes>
76 <total type="fast" count="0" size="0"/>
77 <total type="rest" count="0" size="0"/>
78 <system type="current" size="135168"/>
79 <system type="max" size="135168"/>
80 <aspace type="total" size="135168"/>
81 <aspace type="mprotect" size="135168"/>
82 </heap>
83 <total type="fast" count="0" size="0"/>
84 <total type="rest" count="0" size="0"/>
85 <system type="current" size="135168"/>
86 <system type="max" size="135168"/>
87 <aspace type="total" size="135168"/>
88 <aspace type="mprotect" size="135168"/>
89 </malloc>
90 ============ After allocating blocks ============
92 <malloc version="1">
93 <heap nr="0">
94 <sizes>
95 </sizes>
96 <total type="fast" count="0" size="0"/>
97 <total type="rest" count="0" size="0"/>
98 <system type="current" size="1081344"/>
99 <system type="max" size="1081344"/>
100 <aspace type="total" size="1081344"/>
101 <aspace type="mprotect" size="1081344"/>
102 </heap>
103 <heap nr="1">
104 <sizes>
105 </sizes>
106 <total type="fast" count="0" size="0"/>
107 <total type="rest" count="0" size="0"/>
108 <system type="current" size="1032192"/>
109 <system type="max" size="1032192"/>
110 <aspace type="total" size="1032192"/>
111 <aspace type="mprotect" size="1032192"/>
112 </heap>
113 <total type="fast" count="0" size="0"/>
114 <total type="rest" count="0" size="0"/>
115 <system type="current" size="2113536"/>
116 <system type="max" size="2113536"/>
117 <aspace type="total" size="2113536"/>
118 <aspace type="mprotect" size="2113536"/>
119 </malloc>
120 Program source
122 #include <unistd.h>
123 #include <stdlib.h>
124 #include <pthread.h>
125 #include <malloc.h>
126 #include <errno.h>
127 static size_t blockSize;
129 static int numThreads, numBlocks;
130 #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
132 } while (0)
133 static void *
135 thread_func(void *arg)
136 {
137 int j;
138 int tn = (int) arg;
139 /* The multiplier '(2 + tn)' ensures that each thread (including
141 the main thread) allocates a different amount of memory */
142 for (j = 0; j < numBlocks; j++)
144 if (malloc(blockSize * (2 + tn)) == NULL)
145 errExit("malloc-thread");
146 sleep(100); /* Sleep until main thread terminates */
148 return NULL;
149 }
150 int
152 main(int argc, char *argv[])
153 {
154 int j, tn, sleepTime;
155 pthread_t *thr;
156 if (argc < 4) {
158 fprintf(stderr,
159 "%s num-threads num-blocks block-size [sleep-time]\n",
160 argv[0]);
161 exit(EXIT_FAILURE);
162 }
163 numThreads = atoi(argv[1]);
165 numBlocks = atoi(argv[2]);
166 blockSize = atoi(argv[3]);
167 sleepTime = (argc > 4) ? atoi(argv[4]) : 0;
168 thr = calloc(numThreads, sizeof(pthread_t));
170 if (thr == NULL)
171 errExit("calloc");
172 printf("============ Before allocating blocks ============\n");
174 malloc_info(0, stdout);
175 /* Create threads that allocate different amounts of memory */
177 for (tn = 0; tn < numThreads; tn++) {
179 errno = pthread_create(&thr[tn], NULL, thread_func,
180 (void *) tn);
181 if (errno != 0)
182 errExit("pthread_create");
183 /* If we add a sleep interval after the start-up of each
185 thread, the threads likely won't contend for malloc
186 mutexes, and therefore additional arenas won't be
187 allocated (see malloc(3)). */
188 if (sleepTime > 0)
190 sleep(sleepTime);
191 }
192 /* The main thread also allocates some memory */
194 for (j = 0; j < numBlocks; j++)
196 if (malloc(blockSize) == NULL)
197 errExit("malloc");
198 sleep(2); /* Give all threads a chance to
200 complete allocations */
201 printf("\n============ After allocating blocks ============\n");
203 malloc_info(0, stdout);
204 exit(EXIT_SUCCESS);
206 }
207
209 mallinfo(3), malloc(3), malloc_stats(3), mallopt(3), open_memstream(3)
210
212 This page is part of release 3.53 of the Linux man-pages project. A
213 description of the project, and information about reporting bugs, can
214 be found at http://www.kernel.org/doc/man-pages/.
215GNU 2013-04-19 MALLOC_INFO(3)