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1 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
2 | .\" | |
3 | .\" Permission is granted to make and distribute verbatim copies of this | |
4 | .\" manual provided the copyright notice and this permission notice are | |
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7 | .\" Permission is granted to copy and distribute modified versions of this | |
8 | .\" manual under the conditions for verbatim copying, provided that the | |
9 | .\" entire resulting derived work is distributed under the terms of a | |
10 | .\" permission notice identical to this one. | |
11 | .\" | |
12 | .\" Since the Linux kernel and libraries are constantly changing, this | |
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14 | .\" responsibility for errors or omissions, or for damages resulting from | |
15 | .\" the use of the information contained herein. The author(s) may not | |
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17 | .\" which is licensed free of charge, as they might when working | |
18 | .\" professionally. | |
19 | .\" | |
20 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
21 | .\" the source, must acknowledge the copyright and authors of this work. | |
22 | .\" | |
23 | .TH MALLOC_INFO 3 2012-04-28 "GNU" "Linux Programmer's Manual" | |
24 | .SH NAME | |
25 | malloc_info \- export malloc state to a stream | |
26 | .SH SYNOPSIS | |
27 | .nf | |
28 | .B #include <malloc.h> | |
29 | .sp | |
30 | .BI "int malloc_info(int " options ", FILE *" fp ); | |
31 | .fi | |
32 | .SH DESCRIPTION | |
33 | The | |
34 | .BR malloc_info () | |
35 | function exports an XML string that describes the current state | |
36 | of the memory-allocation | |
37 | implementation in the caller. | |
38 | The string is printed on the file stream | |
39 | .IR fp . | |
40 | The exported string includes information about all arenas (see | |
41 | .BR malloc (3)). | |
42 | ||
43 | As currently implemented, | |
44 | .I options | |
45 | must be zero. | |
46 | .SH RETURN VALUE | |
47 | On success, | |
48 | .BR malloc_info () | |
49 | returns 0; | |
50 | on error, it returns \-1. | |
51 | .SH ERRORS | |
52 | .TP | |
53 | .B EINVAL | |
54 | .I options | |
55 | was nonzero. | |
56 | .SH VERSIONS | |
57 | .BR malloc_info (3) | |
58 | was added to glibc in version 2.10. | |
59 | .SH CONFORMING TO | |
60 | This function is a GNU extension. | |
61 | .SH NOTES | |
62 | The memory-allocation information is provided as an XML string | |
63 | (rather than a C structure) | |
64 | because the information may change over time | |
65 | (according to changes in the underlying implementation). | |
66 | The output XML string includes a version field. | |
67 | ||
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68 | The |
69 | .BR open_memstream (3) | |
70 | function can be used to send the output of | |
71 | .BR malloc_info () | |
72 | directly into a buffer in memory, rather than to a file. | |
73 | ||
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74 | The |
75 | .BR malloc_info () | |
76 | function is designed to address deficiencies in | |
77 | .BR malloc_stats (3) | |
78 | and | |
79 | .BR mallinfo (3). | |
80 | .SH EXAMPLE | |
81 | The program below takes up to four command-line arguments, | |
82 | of which the first three are mandatory. | |
83 | The first argument specifies the number of threads that | |
84 | the program should create. | |
85 | All of the threads, including the main thread, | |
86 | allocate the number of blocks of memory specified by the second argument. | |
87 | The third argument controls the size of the blocks to be allocated. | |
88 | The main thread creates blocks of this size, | |
89 | the second thread created by the program allocates blocks of twice this size, | |
90 | the third thread allocates blocks of three times this size, and so on. | |
91 | ||
92 | The program calls | |
93 | .BR malloc_info () | |
94 | twice to display the memory-allocation state. | |
95 | The first call takes place before any threads | |
96 | are created or memory allocated. | |
97 | The second call is performed after all threads have allocated memory. | |
98 | ||
99 | In the following example, | |
100 | the command-line arguments specify the creation of one additional thread, | |
101 | and both the main thread and the additional thread | |
102 | allocate 10000 blocks of memory. | |
103 | After the blocks of memory have been allocated, | |
104 | .BR malloc_info () | |
105 | shows the state of two allocation arenas. | |
106 | .in +4 | |
107 | .nf | |
108 | ||
109 | .RB "$ " "getconf GNU_LIBC_VERSION" | |
110 | glibc 2.13 | |
111 | .RB "$ " "./a.out 1 10000 100" | |
112 | ============ Before allocating blocks ============ | |
113 | <malloc version="1"> | |
114 | <heap nr="0"> | |
115 | <sizes> | |
116 | </sizes> | |
117 | <total type="fast" count="0" size="0"/> | |
118 | <total type="rest" count="0" size="0"/> | |
119 | <system type="current" size="135168"/> | |
120 | <system type="max" size="135168"/> | |
121 | <aspace type="total" size="135168"/> | |
122 | <aspace type="mprotect" size="135168"/> | |
123 | </heap> | |
124 | <total type="fast" count="0" size="0"/> | |
125 | <total type="rest" count="0" size="0"/> | |
126 | <system type="current" size="135168"/> | |
127 | <system type="max" size="135168"/> | |
128 | <aspace type="total" size="135168"/> | |
129 | <aspace type="mprotect" size="135168"/> | |
130 | </malloc> | |
131 | ||
132 | ============ After allocating blocks ============ | |
133 | <malloc version="1"> | |
134 | <heap nr="0"> | |
135 | <sizes> | |
136 | </sizes> | |
137 | <total type="fast" count="0" size="0"/> | |
138 | <total type="rest" count="0" size="0"/> | |
139 | <system type="current" size="1081344"/> | |
140 | <system type="max" size="1081344"/> | |
141 | <aspace type="total" size="1081344"/> | |
142 | <aspace type="mprotect" size="1081344"/> | |
143 | </heap> | |
144 | <heap nr="1"> | |
145 | <sizes> | |
146 | </sizes> | |
147 | <total type="fast" count="0" size="0"/> | |
148 | <total type="rest" count="0" size="0"/> | |
149 | <system type="current" size="1032192"/> | |
150 | <system type="max" size="1032192"/> | |
151 | <aspace type="total" size="1032192"/> | |
152 | <aspace type="mprotect" size="1032192"/> | |
153 | </heap> | |
154 | <total type="fast" count="0" size="0"/> | |
155 | <total type="rest" count="0" size="0"/> | |
156 | <system type="current" size="2113536"/> | |
157 | <system type="max" size="2113536"/> | |
158 | <aspace type="total" size="2113536"/> | |
159 | <aspace type="mprotect" size="2113536"/> | |
160 | </malloc> | |
161 | .fi | |
162 | .in | |
163 | .SS Program source | |
164 | .nf | |
165 | ||
166 | #include <unistd.h> | |
167 | #include <stdlib.h> | |
168 | #include <pthread.h> | |
169 | #include <malloc.h> | |
170 | #include <errno.h> | |
171 | ||
172 | static size_t blockSize; | |
173 | static int numThreads, numBlocks; | |
174 | ||
175 | #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\ | |
176 | } while (0) | |
177 | ||
178 | static void * | |
179 | thread_func(void *arg) | |
180 | { | |
181 | int j; | |
182 | int tn = (int) arg; | |
183 | ||
184 | /* The multiplier \(aq(2 + tn)\(aq ensures that each thread (including | |
185 | the main thread) allocates a different amount of memory */ | |
186 | ||
187 | for (j = 0; j < numBlocks; j++) | |
188 | if (malloc(blockSize * (2 + tn)) == NULL) | |
189 | errExit("malloc\-thread"); | |
190 | ||
191 | sleep(100); /* Sleep until main thread terminates */ | |
192 | return NULL; | |
193 | } | |
194 | ||
195 | int | |
196 | main(int argc, char *argv[]) | |
197 | { | |
198 | int j, tn, sleepTime; | |
199 | pthread_t *thr; | |
200 | ||
201 | if (argc < 4) { | |
202 | fprintf(stderr, | |
203 | "%s num\-threads num\-blocks block\-size [sleep\-time]\\n", | |
204 | argv[0]); | |
205 | exit(EXIT_FAILURE); | |
206 | } | |
207 | ||
208 | numThreads = atoi(argv[1]); | |
209 | numBlocks = atoi(argv[2]); | |
210 | blockSize = atoi(argv[3]); | |
211 | sleepTime = (argc > 4) ? atoi(argv[4]) : 0; | |
212 | ||
213 | thr = calloc(numThreads, sizeof(pthread_t)); | |
214 | if (thr == NULL) | |
215 | errExit("calloc"); | |
216 | ||
217 | printf("============ Before allocating blocks ============\\n"); | |
218 | malloc_info(0, stdout); | |
219 | ||
220 | /* Create threads that allocate different amounts of memory */ | |
221 | ||
222 | for (tn = 0; tn < numThreads; tn++) { | |
223 | errno = pthread_create(&thr[tn], NULL, thread_func, | |
224 | (void *) tn); | |
225 | if (errno != 0) | |
226 | errExit("pthread_create"); | |
227 | ||
228 | /* If we add a sleep interval after the start\-up of each | |
229 | thread, the threads likely won\(aqt contend for malloc | |
230 | mutexes, and therefore additional arenas won\(aqt be | |
231 | allocated (see malloc(3)). */ | |
232 | ||
233 | if (sleepTime > 0) | |
234 | sleep(sleepTime); | |
235 | } | |
236 | ||
237 | /* The main thread also allocates some memory */ | |
238 | ||
239 | for (j = 0; j < numBlocks; j++) | |
240 | if (malloc(blockSize) == NULL) | |
241 | errExit("malloc"); | |
242 | ||
243 | sleep(2); /* Give all threads a chance to | |
244 | complete allocations */ | |
245 | ||
246 | printf("\\n============ After allocating blocks ============\\n"); | |
247 | malloc_info(0, stdout); | |
248 | ||
249 | exit(EXIT_SUCCESS); | |
250 | } | |
251 | .fi | |
252 | .SH SEE ALSO | |
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253 | .BR mallinfo (3), |
254 | .BR malloc (3), | |
255 | .BR malloc_stats (3), | |
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256 | .BR mallopt (3), |
257 | .BR open_memstream (3) |