Using Memory Use Checking

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Memory use checking enables you to see all the heap memory in use. You can use this information to get a sense of where memory is allocated in your program or which program sections are using the most dynamic memory. This information can also be useful in reducing the dynamic memory consumption of your program and might help in performance tuning.

Memory use checking is useful during performance tuning or to control virtual memory use. When the program exits, a memory use report can be generated. Memory usage information can also be obtained at any time during program execution with the showmemuse command, which causes memory usage to be displayed. For information, see showmemuse Command.

Enabling memory use checking also enables leak checking. In addition to a leak report at the program exit, you also get a Blocks in use (biu) report. By default, a non-verbose blocks in use report is generated at program exit. The level of detail in the memory use report is controlled by the dbxenv variable rtc_biu_at_exit.

The following example shows a typical non-verbose memory use report.

Blocks in use report   (blocks in use: 5   total size:   40 bytes)

 Total     % of Num of  Avg     Allocation call stack
 Size       All Blocks  Size
========== ==== ====== ======  =====================================
        16  40%      2      8  nonleak < nonleak
         8  20%      1      8  nonleak < main
         8  20%      1      8  cyclic_leaks < main
         8  20%      1      8  cyclic_leaks < main

Blocks in use report   (blocks in use: 5   total size:   40 bytes)

Block in use (biu):
Found 2 blocks totaling 16 bytes (40.00% of total; avg block size 8)
At time of each allocation, the call stack was:
     [1] nonleak() at line 182 in "memuse.c"
     [2] nonleak() at line 185 in "memuse.c"

Block in use (biu):
Found block of size 8 bytes at address 0x21898 (20.00% of total)
At time of allocation, the call stack was:
     [1] nonleak() at line 182 in "memuse.c"
     [2] main() at line 74 in "memuse.c"

Block in use (biu):
Found block of size 8 bytes at address 0x21958 (20.00% of total)
At time of allocation, the call stack was:
     [1] cyclic_leaks() at line 154 in "memuse.c"
     [2] main() at line 118 in "memuse.c"

Block in use (biu):
Found block of size 8 bytes at address 0x21978 (20.00% of total)
At time of allocation, the call stack was:
     [1] cyclic_leaks() at line 155 in "memuse.c"
     [2] main() at line 118 in "memuse.c"
The following is the corresponding verbose memory use report:

You can ask for a memory use report any time with the showmemuse command.