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62d874a0 | 1 | '\" t |
3c81c5a4 | 2 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
62d874a0 | 3 | .\" |
93015253 | 4 | .\" %%%LICENSE_START(VERBATIM) |
62d874a0 MK |
5 | .\" Permission is granted to make and distribute verbatim copies of this |
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12 | .\" permission notice identical to this one. | |
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4b72fb64 | 24 | .\" %%%LICENSE_END |
62d874a0 | 25 | .\" |
4b8c67d9 | 26 | .TH MALLINFO 3 2017-09-15 "Linux" "Linux Programmer's Manual" |
62d874a0 MK |
27 | .SH NAME |
28 | mallinfo \- obtain memory allocation information | |
29 | .SH SYNOPSIS | |
30 | .B #include <malloc.h> | |
f90f031e | 31 | .PP |
62d874a0 MK |
32 | .B struct mallinfo mallinfo(void); |
33 | .SH DESCRIPTION | |
34 | The | |
35 | .BR mallinfo () | |
36 | function returns a copy of a structure containing information about | |
37 | memory allocations performed by | |
38 | .BR malloc (3) | |
39 | and related functions. | |
40 | This structure is defined as follows: | |
41 | .PP | |
42 | .in +4n | |
b8302363 | 43 | .EX |
62d874a0 MK |
44 | struct mallinfo { |
45 | int arena; /* Non-mmapped space allocated (bytes) */ | |
46 | int ordblks; /* Number of free chunks */ | |
47 | int smblks; /* Number of free fastbin blocks */ | |
48 | int hblks; /* Number of mmapped regions */ | |
49 | int hblkhd; /* Space allocated in mmapped regions (bytes) */ | |
50 | int usmblks; /* Maximum total allocated space (bytes) */ | |
51 | int fsmblks; /* Space in freed fastbin blocks (bytes) */ | |
52 | int uordblks; /* Total allocated space (bytes) */ | |
53 | int fordblks; /* Total free space (bytes) */ | |
54 | int keepcost; /* Top-most, releasable space (bytes) */ | |
55 | }; | |
b8302363 | 56 | .EE |
62d874a0 MK |
57 | .in |
58 | .PP | |
59 | The fields of the | |
60 | .I mallinfo | |
61 | structure contain the following information: | |
62d874a0 MK |
62 | .TP 10 |
63 | .I arena | |
64 | The total amount of memory allocated by means other than | |
65 | .BR mmap (2) | |
66 | (i.e., memory allocated on the heap). | |
67 | This figure includes both in-use blocks and blocks on the free list. | |
68 | .TP | |
69 | .I ordblks | |
70 | The number of ordinary (i.e., non-fastbin) free blocks. | |
71 | .TP | |
72 | .I smblks | |
73 | The number of fastbin free blocks (see | |
74 | .BR mallopt (3)). | |
75 | .TP | |
76 | .I hblks | |
77 | The number of blocks currently allocated using | |
78 | .BR mmap (2). | |
35af1345 MK |
79 | (See the discussion of |
80 | .B M_MMAP_THRESHOLD | |
81 | in | |
82 | .BR mallopt (3).) | |
62d874a0 MK |
83 | .TP |
84 | .I hblkhd | |
85 | The number of bytes in blocks currently allocated using | |
86 | .BR mmap (2). | |
87 | .TP | |
88 | .I usmblks | |
89 | The "highwater mark" for allocated space\(emthat is, | |
90 | the maximum amount of space that was ever allocated. | |
91 | This field is maintained only in nonthreading environments. | |
92 | .TP | |
93 | .I fsmblks | |
94 | The total number of bytes in fastbin free blocks. | |
95 | .TP | |
96 | .I uordblks | |
97 | The total number of bytes used by in-use allocations. | |
98 | .TP | |
99 | .I fordblks | |
100 | The total number of bytes in free blocks. | |
101 | .TP | |
102 | .I keepcost | |
103 | The total amount of releasable free space at the top | |
104 | of the heap. | |
105 | This is the maximum number of bytes that could ideally | |
106 | (i.e., ignoring page alignment restrictions, and so on) be released by | |
107 | .BR malloc_trim (3). | |
108 | .\" .SH VERSIONS | |
109 | .\" Available already in glibc 2.0, possibly earlier | |
c32cf268 ZL |
110 | .SH ATTRIBUTES |
111 | For an explanation of the terms used in this section, see | |
112 | .BR attributes (7). | |
113 | .TS | |
114 | allbox; | |
115 | lb lb lbw28 | |
116 | l l l. | |
117 | Interface Attribute Value | |
118 | T{ | |
119 | .BR mallinfo () | |
120 | T} Thread safety MT-Unsafe init const:mallopt | |
121 | .TE | |
847e0d88 | 122 | .sp 1 |
c32cf268 | 123 | .BR mallinfo () |
696bd2da MK |
124 | would access some global internal objects. |
125 | If modify them with non-atomically, | |
c32cf268 ZL |
126 | may get inconsistent results. |
127 | The identifier | |
128 | .I mallopt | |
129 | in | |
130 | .I const:mallopt | |
131 | mean that | |
132 | .BR mallopt () | |
3c841730 | 133 | would modify the global internal objects with atomics, that make sure |
c32cf268 ZL |
134 | .BR mallinfo () |
135 | is safe enough, others modify with non-atomically maybe not. | |
62d874a0 MK |
136 | .SH CONFORMING TO |
137 | This function is not specified by POSIX or the C standards. | |
138 | A similar function exists on many System V derivatives, | |
139 | and was specified in the SVID. | |
f704bc68 | 140 | .SH BUGS |
bea08fec | 141 | .\" FIXME . http://sourceware.org/bugzilla/show_bug.cgi?id=208 |
f704bc68 MK |
142 | .\" See the 24 Aug 2011 mail by Paul Pluzhnikov: |
143 | .\" "[patch] Fix mallinfo() to accumulate results for all arenas" | |
144 | .\" on libc-alpha@sourceware.org | |
3c81c5a4 MK |
145 | .B Information is returned for only the main memory allocation area. |
146 | Allocations in other arenas are excluded. | |
147 | See | |
148 | .BR malloc_stats (3) | |
149 | and | |
150 | .BR malloc_info (3) | |
151 | for alternatives that include information about other arenas. | |
847e0d88 | 152 | .PP |
62d874a0 MK |
153 | The fields of the |
154 | .I mallinfo | |
155 | structure are typed as | |
156 | .IR int . | |
157 | However, because some internal bookkeeping values may be of type | |
158 | .IR long , | |
159 | the reported values may wrap around zero and thus be inaccurate. | |
160 | .SH EXAMPLE | |
161 | The program below employs | |
162 | .BR mallinfo () | |
163 | to retrieve memory allocation statistics before and after | |
164 | allocating and freeing some blocks of memory. | |
165 | The statistics are displayed on standard output. | |
847e0d88 | 166 | .PP |
62d874a0 MK |
167 | The first two command-line arguments specify the number and size of |
168 | blocks to be allocated with | |
169 | .BR malloc (3). | |
847e0d88 | 170 | .PP |
62d874a0 MK |
171 | The remaining three arguments specify which of the allocated blocks |
172 | should be freed with | |
173 | .BR free (3). | |
174 | These three arguments are optional, and specify (in order): | |
175 | the step size to be used in the loop that frees blocks | |
176 | (the default is 1, meaning free all blocks in the range); | |
177 | the ordinal position of the first block to be freed | |
178 | (default 0, meaning the first allocated block); | |
179 | and a number one greater than the ordinal position | |
180 | of the last block to be freed | |
181 | (default is one greater than the maximum block number). | |
182 | If these three arguments are omitted, | |
183 | then the defaults cause all allocated blocks to be freed. | |
847e0d88 | 184 | .PP |
62d874a0 MK |
185 | In the following example run of the program, |
186 | 1000 allocations of 100 bytes are performed, | |
187 | and then every second allocated block is freed: | |
188 | .PP | |
189 | .in +4n | |
b8302363 | 190 | .EX |
62d874a0 MK |
191 | $ \fB./a.out 1000 100 2\fP |
192 | ============== Before allocating blocks ============== | |
193 | Total non\-mmapped bytes (arena): 0 | |
194 | # of free chunks (ordblks): 1 | |
195 | # of free fastbin blocks (smblks): 0 | |
196 | # of mapped regions (hblks): 0 | |
197 | Bytes in mapped regions (hblkhd): 0 | |
198 | Max. total allocated space (usmblks): 0 | |
199 | Free bytes held in fastbins (fsmblks): 0 | |
200 | Total allocated space (uordblks): 0 | |
201 | Total free space (fordblks): 0 | |
202 | Topmost releasable block (keepcost): 0 | |
203 | ||
204 | ============== After allocating blocks ============== | |
205 | Total non\-mmapped bytes (arena): 135168 | |
206 | # of free chunks (ordblks): 1 | |
207 | # of free fastbin blocks (smblks): 0 | |
208 | # of mapped regions (hblks): 0 | |
209 | Bytes in mapped regions (hblkhd): 0 | |
210 | Max. total allocated space (usmblks): 0 | |
211 | Free bytes held in fastbins (fsmblks): 0 | |
212 | Total allocated space (uordblks): 104000 | |
213 | Total free space (fordblks): 31168 | |
214 | Topmost releasable block (keepcost): 31168 | |
215 | ||
216 | ============== After freeing blocks ============== | |
217 | Total non\-mmapped bytes (arena): 135168 | |
218 | # of free chunks (ordblks): 501 | |
219 | # of free fastbin blocks (smblks): 0 | |
220 | # of mapped regions (hblks): 0 | |
221 | Bytes in mapped regions (hblkhd): 0 | |
222 | Max. total allocated space (usmblks): 0 | |
223 | Free bytes held in fastbins (fsmblks): 0 | |
224 | Total allocated space (uordblks): 52000 | |
225 | Total free space (fordblks): 83168 | |
226 | Topmost releasable block (keepcost): 31168 | |
b8302363 | 227 | .EE |
62d874a0 MK |
228 | .in |
229 | .SS Program source | |
230 | \& | |
e7d0bb47 | 231 | .EX |
62d874a0 | 232 | #include <malloc.h> |
e40be343 JW |
233 | #include <stdlib.h> |
234 | #include <string.h> | |
62d874a0 MK |
235 | |
236 | static void | |
237 | display_mallinfo(void) | |
238 | { | |
239 | struct mallinfo mi; | |
240 | ||
241 | mi = mallinfo(); | |
242 | ||
243 | printf("Total non\-mmapped bytes (arena): %d\\n", mi.arena); | |
244 | printf("# of free chunks (ordblks): %d\\n", mi.ordblks); | |
245 | printf("# of free fastbin blocks (smblks): %d\\n", mi.smblks); | |
246 | printf("# of mapped regions (hblks): %d\\n", mi.hblks); | |
247 | printf("Bytes in mapped regions (hblkhd): %d\\n", mi.hblkhd); | |
248 | printf("Max. total allocated space (usmblks): %d\\n", mi.usmblks); | |
249 | printf("Free bytes held in fastbins (fsmblks): %d\\n", mi.fsmblks); | |
250 | printf("Total allocated space (uordblks): %d\\n", mi.uordblks); | |
251 | printf("Total free space (fordblks): %d\\n", mi.fordblks); | |
252 | printf("Topmost releasable block (keepcost): %d\\n", mi.keepcost); | |
253 | } | |
254 | ||
255 | int | |
256 | main(int argc, char *argv[]) | |
257 | { | |
258 | #define MAX_ALLOCS 2000000 | |
259 | char *alloc[MAX_ALLOCS]; | |
260 | int numBlocks, j, freeBegin, freeEnd, freeStep; | |
261 | size_t blockSize; | |
262 | ||
e40be343 JW |
263 | if (argc < 3 || strcmp(argv[1], "\-\-help") == 0) { |
264 | fprintf(stderr, "%s num\-blocks block\-size [free\-step " | |
265 | "[start\-free [end\-free]]]\\n", argv[0]); | |
266 | exit(EXIT_FAILURE); | |
267 | } | |
62d874a0 MK |
268 | |
269 | numBlocks = atoi(argv[1]); | |
270 | blockSize = atoi(argv[2]); | |
271 | freeStep = (argc > 3) ? atoi(argv[3]) : 1; | |
272 | freeBegin = (argc > 4) ? atoi(argv[4]) : 0; | |
273 | freeEnd = (argc > 5) ? atoi(argv[5]) : numBlocks; | |
274 | ||
275 | printf("============== Before allocating blocks ==============\\n"); | |
276 | display_mallinfo(); | |
277 | ||
278 | for (j = 0; j < numBlocks; j++) { | |
e40be343 JW |
279 | if (numBlocks >= MAX_ALLOCS) { |
280 | fprintf(stderr, "Too many allocations\\n"); | |
281 | exit(EXIT_FAILURE); | |
282 | } | |
62d874a0 MK |
283 | |
284 | alloc[j] = malloc(blockSize); | |
e40be343 JW |
285 | if (alloc[j] == NULL) { |
286 | perror("malloc"); | |
287 | exit(EXIT_FAILURE); | |
288 | } | |
62d874a0 MK |
289 | } |
290 | ||
291 | printf("\\n============== After allocating blocks ==============\\n"); | |
292 | display_mallinfo(); | |
293 | ||
294 | for (j = freeBegin; j < freeEnd; j += freeStep) | |
295 | free(alloc[j]); | |
296 | ||
297 | printf("\\n============== After freeing blocks ==============\\n"); | |
298 | display_mallinfo(); | |
299 | ||
300 | exit(EXIT_SUCCESS); | |
301 | } | |
e7d0bb47 | 302 | .EE |
62d874a0 MK |
303 | .SH SEE ALSO |
304 | .ad l | |
305 | .nh | |
306 | .BR mmap (2), | |
307 | .BR malloc (3), | |
3c81c5a4 | 308 | .BR malloc_info (3), |
62d874a0 MK |
309 | .BR malloc_stats (3), |
310 | .BR malloc_trim (3), | |
311 | .BR mallopt (3) |