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25 .TH MALLOC_INFO 3 2012-04-28 "GNU" "Linux Programmer's Manual"
27 malloc_info \- export malloc state to a stream
30 .B #include <malloc.h>
32 .BI "int malloc_info(int " options ", FILE *" fp );
37 function exports an XML string that describes the current state
38 of the memory-allocation
39 implementation in the caller.
40 The string is printed on the file stream
42 The exported string includes information about all arenas (see
45 As currently implemented,
52 on error, it returns \-1.
60 was added to glibc in version 2.10.
62 This function is a GNU extension.
64 The memory-allocation information is provided as an XML string
65 (rather than a C structure)
66 because the information may change over time
67 (according to changes in the underlying implementation).
68 The output XML string includes a version field.
71 .BR open_memstream (3)
72 function can be used to send the output of
74 directly into a buffer in memory, rather than to a file.
78 function is designed to address deficiencies in
83 The program below takes up to four command-line arguments,
84 of which the first three are mandatory.
85 The first argument specifies the number of threads that
86 the program should create.
87 All of the threads, including the main thread,
88 allocate the number of blocks of memory specified by the second argument.
89 The third argument controls the size of the blocks to be allocated.
90 The main thread creates blocks of this size,
91 the second thread created by the program allocates blocks of twice this size,
92 the third thread allocates blocks of three times this size, and so on.
96 twice to display the memory-allocation state.
97 The first call takes place before any threads
98 are created or memory allocated.
99 The second call is performed after all threads have allocated memory.
101 In the following example,
102 the command-line arguments specify the creation of one additional thread,
103 and both the main thread and the additional thread
104 allocate 10000 blocks of memory.
105 After the blocks of memory have been allocated,
107 shows the state of two allocation arenas.
111 .RB "$ " "getconf GNU_LIBC_VERSION"
113 .RB "$ " "./a.out 1 10000 100"
114 ============ Before allocating blocks ============
119 <total type="fast" count="0" size="0"/>
120 <total type="rest" count="0" size="0"/>
121 <system type="current" size="135168"/>
122 <system type="max" size="135168"/>
123 <aspace type="total" size="135168"/>
124 <aspace type="mprotect" size="135168"/>
126 <total type="fast" count="0" size="0"/>
127 <total type="rest" count="0" size="0"/>
128 <system type="current" size="135168"/>
129 <system type="max" size="135168"/>
130 <aspace type="total" size="135168"/>
131 <aspace type="mprotect" size="135168"/>
134 ============ After allocating blocks ============
139 <total type="fast" count="0" size="0"/>
140 <total type="rest" count="0" size="0"/>
141 <system type="current" size="1081344"/>
142 <system type="max" size="1081344"/>
143 <aspace type="total" size="1081344"/>
144 <aspace type="mprotect" size="1081344"/>
149 <total type="fast" count="0" size="0"/>
150 <total type="rest" count="0" size="0"/>
151 <system type="current" size="1032192"/>
152 <system type="max" size="1032192"/>
153 <aspace type="total" size="1032192"/>
154 <aspace type="mprotect" size="1032192"/>
156 <total type="fast" count="0" size="0"/>
157 <total type="rest" count="0" size="0"/>
158 <system type="current" size="2113536"/>
159 <system type="max" size="2113536"/>
160 <aspace type="total" size="2113536"/>
161 <aspace type="mprotect" size="2113536"/>
174 static size_t blockSize;
175 static int numThreads, numBlocks;
177 #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\
181 thread_func(void *arg)
186 /* The multiplier \(aq(2 + tn)\(aq ensures that each thread (including
187 the main thread) allocates a different amount of memory */
189 for (j = 0; j < numBlocks; j++)
190 if (malloc(blockSize * (2 + tn)) == NULL)
191 errExit("malloc\-thread");
193 sleep(100); /* Sleep until main thread terminates */
198 main(int argc, char *argv[])
200 int j, tn, sleepTime;
205 "%s num\-threads num\-blocks block\-size [sleep\-time]\\n",
210 numThreads = atoi(argv[1]);
211 numBlocks = atoi(argv[2]);
212 blockSize = atoi(argv[3]);
213 sleepTime = (argc > 4) ? atoi(argv[4]) : 0;
215 thr = calloc(numThreads, sizeof(pthread_t));
219 printf("============ Before allocating blocks ============\\n");
220 malloc_info(0, stdout);
222 /* Create threads that allocate different amounts of memory */
224 for (tn = 0; tn < numThreads; tn++) {
225 errno = pthread_create(&thr[tn], NULL, thread_func,
228 errExit("pthread_create");
230 /* If we add a sleep interval after the start\-up of each
231 thread, the threads likely won\(aqt contend for malloc
232 mutexes, and therefore additional arenas won\(aqt be
233 allocated (see malloc(3)). */
239 /* The main thread also allocates some memory */
241 for (j = 0; j < numBlocks; j++)
242 if (malloc(blockSize) == NULL)
245 sleep(2); /* Give all threads a chance to
246 complete allocations */
248 printf("\\n============ After allocating blocks ============\\n");
249 malloc_info(0, stdout);
257 .BR malloc_stats (3),
259 .BR open_memstream (3)