man3/malloc_info.3

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  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
  68 The
  69 .BR malloc_info ()
  70 function is designed to address deficiencies in
  71 .BR malloc_stats (3)
  72 and
  73 .BR mallinfo (3).
  74 .SH EXAMPLE
  75 The program below takes up to four command-line arguments,
  76 of which the first three are mandatory.
  77 The first argument specifies the number of threads that
  78 the program should create.
  79 All of the threads, including the main thread,
  80 allocate the number of blocks of memory specified by the second argument.
  81 The third argument controls the size of the blocks to be allocated.
  82 The main thread creates blocks of this size,
  83 the second thread created by the program allocates blocks of twice this size,
  84 the third thread allocates blocks of three times this size, and so on.
  85
  86 The program calls
  87 .BR malloc_info ()
  88 twice to display the memory-allocation state.
  89 The first call takes place before any threads
  90 are created or memory allocated.
  91 The second call is performed after all threads have allocated memory.
  92
  93 In the following example,
  94 the command-line arguments specify the creation of one additional thread,
  95 and both the main thread and the additional thread
  96 allocate 10000 blocks of memory.
  97 After the blocks of memory have been allocated,
  98 .BR malloc_info ()
  99 shows the state of two allocation arenas.
 100 .in +4
 101 .nf
 102
 103 .RB "$ " "getconf GNU_LIBC_VERSION"
 104 glibc 2.13
 105 .RB "$ " "./a.out 1 10000 100"
 106 ============ Before allocating blocks ============
 107 <malloc version="1">
 108 <heap nr="0">
 109 <sizes>
 110 </sizes>
 111 <total type="fast" count="0" size="0"/>
 112 <total type="rest" count="0" size="0"/>
 113 <system type="current" size="135168"/>
 114 <system type="max" size="135168"/>
 115 <aspace type="total" size="135168"/>
 116 <aspace type="mprotect" size="135168"/>
 117 </heap>
 118 <total type="fast" count="0" size="0"/>
 119 <total type="rest" count="0" size="0"/>
 120 <system type="current" size="135168"/>
 121 <system type="max" size="135168"/>
 122 <aspace type="total" size="135168"/>
 123 <aspace type="mprotect" size="135168"/>
 124 </malloc>
 125
 126 ============ After allocating blocks ============
 127 <malloc version="1">
 128 <heap nr="0">
 129 <sizes>
 130 </sizes>
 131 <total type="fast" count="0" size="0"/>
 132 <total type="rest" count="0" size="0"/>
 133 <system type="current" size="1081344"/>
 134 <system type="max" size="1081344"/>
 135 <aspace type="total" size="1081344"/>
 136 <aspace type="mprotect" size="1081344"/>
 137 </heap>
 138 <heap nr="1">
 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="1032192"/>
 144 <system type="max" size="1032192"/>
 145 <aspace type="total" size="1032192"/>
 146 <aspace type="mprotect" size="1032192"/>
 147 </heap>
 148 <total type="fast" count="0" size="0"/>
 149 <total type="rest" count="0" size="0"/>
 150 <system type="current" size="2113536"/>
 151 <system type="max" size="2113536"/>
 152 <aspace type="total" size="2113536"/>
 153 <aspace type="mprotect" size="2113536"/>
 154 </malloc>
 155 .fi
 156 .in
 157 .SS Program source
 158 .nf
 159
 160 #include <unistd.h>
 161 #include <stdlib.h>
 162 #include <pthread.h>
 163 #include <malloc.h>
 164 #include <errno.h>
 165
 166 static size_t blockSize;
 167 static int numThreads, numBlocks;
 168
 169 #define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \\
 170                         } while (0)
 171
 172 static void *
 173 thread_func(void *arg)
 174 {
 175     int j;
 176     int tn = (int) arg;
 177
 178     /* The multiplier \(aq(2 + tn)\(aq ensures that each thread (including
 179        the main thread) allocates a different amount of memory */
 180
 181     for (j = 0; j < numBlocks; j++)
 182         if (malloc(blockSize * (2 + tn)) == NULL)
 183             errExit("malloc\-thread");
 184
 185     sleep(100);         /* Sleep until main thread terminates */
 186     return NULL;
 187 }
 188
 189 int
 190 main(int argc, char *argv[])
 191 {
 192     int j, tn, sleepTime;
 193     pthread_t *thr;
 194
 195     if (argc < 4) {
 196         fprintf(stderr,
 197                 "%s num\-threads num\-blocks block\-size [sleep\-time]\\n",
 198                 argv[0]);
 199         exit(EXIT_FAILURE);
 200     }
 201
 202     numThreads = atoi(argv[1]);
 203     numBlocks = atoi(argv[2]);
 204     blockSize = atoi(argv[3]);
 205     sleepTime = (argc > 4) ? atoi(argv[4]) : 0;
 206
 207     thr = calloc(numThreads, sizeof(pthread_t));
 208     if (thr == NULL)
 209         errExit("calloc");
 210
 211     printf("============ Before allocating blocks ============\\n");
 212     malloc_info(0, stdout);
 213
 214     /* Create threads that allocate different amounts of memory */
 215
 216     for (tn = 0; tn < numThreads; tn++) {
 217         errno = pthread_create(&thr[tn], NULL, thread_func,
 218                                (void *) tn);
 219         if (errno != 0)
 220             errExit("pthread_create");
 221
 222         /* If we add a sleep interval after the start\-up of each
 223            thread, the threads likely won\(aqt contend for malloc
 224            mutexes, and therefore additional arenas won\(aqt be
 225            allocated (see malloc(3)). */
 226
 227         if (sleepTime > 0)
 228             sleep(sleepTime);
 229     }
 230
 231     /* The main thread also allocates some memory */
 232
 233     for (j = 0; j < numBlocks; j++)
 234         if (malloc(blockSize) == NULL)
 235             errExit("malloc");
 236
 237     sleep(2);           /* Give all threads a chance to
 238                            complete allocations */
 239
 240     printf("\\n============ After allocating blocks ============\\n");
 241     malloc_info(0, stdout);
 242
 243     exit(EXIT_SUCCESS);
 244 }
 245 .fi
 246 .SH SEE ALSO
 247 .BR fmemopen (3),
 248 .BR mallinfo (3),
 249 .BR malloc (3),
 250 .BR malloc_stats (3),
 251 .BR mallopt (3)