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1 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
2 | .\" | |
93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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4 | .\" Permission is granted to make and distribute verbatim copies of this |
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4b72fb64 | 23 | .\" %%%LICENSE_END |
47c31183 | 24 | .\" |
921dd685 | 25 | .TH MALLOC_INFO 3 2013-04-19 "GNU" "Linux Programmer's Manual" |
47c31183 MK |
26 | .SH NAME |
27 | malloc_info \- export malloc state to a stream | |
28 | .SH SYNOPSIS | |
29 | .nf | |
30 | .B #include <malloc.h> | |
31 | .sp | |
91f8edd6 | 32 | .BI "int malloc_info(int " options ", FILE *" stream ); |
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33 | .fi |
34 | .SH DESCRIPTION | |
35 | The | |
36 | .BR malloc_info () | |
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 | |
91f8edd6 | 41 | .IR stream . |
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42 | The exported string includes information about all arenas (see |
43 | .BR malloc (3)). | |
44 | ||
45 | As currently implemented, | |
46 | .I options | |
47 | must be zero. | |
48 | .SH RETURN VALUE | |
49 | On success, | |
50 | .BR malloc_info () | |
51 | returns 0; | |
921dd685 MK |
52 | on error, it returns \-1, with |
53 | .I errno | |
54 | set to indicate the cause. | |
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55 | .SH ERRORS |
56 | .TP | |
57 | .B EINVAL | |
58 | .I options | |
59 | was nonzero. | |
60 | .SH VERSIONS | |
42a6569e | 61 | .BR malloc_info () |
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62 | was added to glibc in version 2.10. |
63 | .SH CONFORMING TO | |
64 | This function is a GNU extension. | |
65 | .SH NOTES | |
66 | The memory-allocation information is provided as an XML string | |
67 | (rather than a C structure) | |
68 | because the information may change over time | |
69 | (according to changes in the underlying implementation). | |
70 | The output XML string includes a version field. | |
71 | ||
a5cbea5f MK |
72 | The |
73 | .BR open_memstream (3) | |
74 | function can be used to send the output of | |
75 | .BR malloc_info () | |
76 | directly into a buffer in memory, rather than to a file. | |
77 | ||
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78 | The |
79 | .BR malloc_info () | |
80 | function is designed to address deficiencies in | |
81 | .BR malloc_stats (3) | |
82 | and | |
83 | .BR mallinfo (3). | |
84 | .SH EXAMPLE | |
85 | The program below takes up to four command-line arguments, | |
86 | of which the first three are mandatory. | |
87 | The first argument specifies the number of threads that | |
88 | the program should create. | |
89 | All of the threads, including the main thread, | |
90 | allocate the number of blocks of memory specified by the second argument. | |
91 | The third argument controls the size of the blocks to be allocated. | |
92 | The main thread creates blocks of this size, | |
93 | the second thread created by the program allocates blocks of twice this size, | |
94 | the third thread allocates blocks of three times this size, and so on. | |
95 | ||
96 | The program calls | |
97 | .BR malloc_info () | |
98 | twice to display the memory-allocation state. | |
99 | The first call takes place before any threads | |
100 | are created or memory allocated. | |
101 | The second call is performed after all threads have allocated memory. | |
102 | ||
103 | In the following example, | |
104 | the command-line arguments specify the creation of one additional thread, | |
105 | and both the main thread and the additional thread | |
106 | allocate 10000 blocks of memory. | |
107 | After the blocks of memory have been allocated, | |
108 | .BR malloc_info () | |
109 | shows the state of two allocation arenas. | |
110 | .in +4 | |
111 | .nf | |
112 | ||
113 | .RB "$ " "getconf GNU_LIBC_VERSION" | |
114 | glibc 2.13 | |
115 | .RB "$ " "./a.out 1 10000 100" | |
116 | ============ Before allocating blocks ============ | |
117 | <malloc version="1"> | |
118 | <heap nr="0"> | |
119 | <sizes> | |
120 | </sizes> | |
121 | <total type="fast" count="0" size="0"/> | |
122 | <total type="rest" count="0" size="0"/> | |
123 | <system type="current" size="135168"/> | |
124 | <system type="max" size="135168"/> | |
125 | <aspace type="total" size="135168"/> | |
126 | <aspace type="mprotect" size="135168"/> | |
127 | </heap> | |
128 | <total type="fast" count="0" size="0"/> | |
129 | <total type="rest" count="0" size="0"/> | |
130 | <system type="current" size="135168"/> | |
131 | <system type="max" size="135168"/> | |
132 | <aspace type="total" size="135168"/> | |
133 | <aspace type="mprotect" size="135168"/> | |
134 | </malloc> | |
135 | ||
136 | ============ After allocating blocks ============ | |
137 | <malloc version="1"> | |
138 | <heap nr="0"> | |
139 | <sizes> | |
140 | </sizes> | |
141 | <total type="fast" count="0" size="0"/> | |
142 | <total type="rest" count="0" size="0"/> | |
143 | <system type="current" size="1081344"/> | |
144 | <system type="max" size="1081344"/> | |
145 | <aspace type="total" size="1081344"/> | |
146 | <aspace type="mprotect" size="1081344"/> | |
147 | </heap> | |
148 | <heap nr="1"> | |
149 | <sizes> | |
150 | </sizes> | |
151 | <total type="fast" count="0" size="0"/> | |
152 | <total type="rest" count="0" size="0"/> | |
153 | <system type="current" size="1032192"/> | |
154 | <system type="max" size="1032192"/> | |
155 | <aspace type="total" size="1032192"/> | |
156 | <aspace type="mprotect" size="1032192"/> | |
157 | </heap> | |
158 | <total type="fast" count="0" size="0"/> | |
159 | <total type="rest" count="0" size="0"/> | |
160 | <system type="current" size="2113536"/> | |
161 | <system type="max" size="2113536"/> | |
162 | <aspace type="total" size="2113536"/> | |
163 | <aspace type="mprotect" size="2113536"/> | |
164 | </malloc> | |
165 | .fi | |
166 | .in | |
167 | .SS Program source | |
168 | .nf | |
169 | ||
170 | #include <unistd.h> | |
171 | #include <stdlib.h> | |
172 | #include <pthread.h> | |
173 | #include <malloc.h> | |
174 | #include <errno.h> | |
175 | ||
176 | static size_t blockSize; | |
177 | static int numThreads, numBlocks; | |
178 | ||
179 | #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\ | |
180 | } while (0) | |
181 | ||
182 | static void * | |
183 | thread_func(void *arg) | |
184 | { | |
185 | int j; | |
186 | int tn = (int) arg; | |
187 | ||
188 | /* The multiplier \(aq(2 + tn)\(aq ensures that each thread (including | |
189 | the main thread) allocates a different amount of memory */ | |
190 | ||
191 | for (j = 0; j < numBlocks; j++) | |
192 | if (malloc(blockSize * (2 + tn)) == NULL) | |
193 | errExit("malloc\-thread"); | |
194 | ||
195 | sleep(100); /* Sleep until main thread terminates */ | |
196 | return NULL; | |
197 | } | |
198 | ||
199 | int | |
200 | main(int argc, char *argv[]) | |
201 | { | |
202 | int j, tn, sleepTime; | |
203 | pthread_t *thr; | |
204 | ||
205 | if (argc < 4) { | |
206 | fprintf(stderr, | |
207 | "%s num\-threads num\-blocks block\-size [sleep\-time]\\n", | |
208 | argv[0]); | |
209 | exit(EXIT_FAILURE); | |
210 | } | |
211 | ||
212 | numThreads = atoi(argv[1]); | |
213 | numBlocks = atoi(argv[2]); | |
214 | blockSize = atoi(argv[3]); | |
215 | sleepTime = (argc > 4) ? atoi(argv[4]) : 0; | |
216 | ||
217 | thr = calloc(numThreads, sizeof(pthread_t)); | |
218 | if (thr == NULL) | |
219 | errExit("calloc"); | |
220 | ||
221 | printf("============ Before allocating blocks ============\\n"); | |
222 | malloc_info(0, stdout); | |
223 | ||
224 | /* Create threads that allocate different amounts of memory */ | |
225 | ||
226 | for (tn = 0; tn < numThreads; tn++) { | |
227 | errno = pthread_create(&thr[tn], NULL, thread_func, | |
228 | (void *) tn); | |
229 | if (errno != 0) | |
230 | errExit("pthread_create"); | |
231 | ||
232 | /* If we add a sleep interval after the start\-up of each | |
233 | thread, the threads likely won\(aqt contend for malloc | |
234 | mutexes, and therefore additional arenas won\(aqt be | |
235 | allocated (see malloc(3)). */ | |
236 | ||
237 | if (sleepTime > 0) | |
238 | sleep(sleepTime); | |
239 | } | |
240 | ||
241 | /* The main thread also allocates some memory */ | |
0ab8aeec | 242 | |
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243 | for (j = 0; j < numBlocks; j++) |
244 | if (malloc(blockSize) == NULL) | |
245 | errExit("malloc"); | |
246 | ||
247 | sleep(2); /* Give all threads a chance to | |
248 | complete allocations */ | |
249 | ||
250 | printf("\\n============ After allocating blocks ============\\n"); | |
251 | malloc_info(0, stdout); | |
252 | ||
253 | exit(EXIT_SUCCESS); | |
254 | } | |
255 | .fi | |
256 | .SH SEE ALSO | |
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257 | .BR mallinfo (3), |
258 | .BR malloc (3), | |
259 | .BR malloc_stats (3), | |
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260 | .BR mallopt (3), |
261 | .BR open_memstream (3) |