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POValgrind understanding bytes allocated increase in heap summary?
 

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  1. POValgrind understanding bytes allocated increase in heap summary?
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    <p>I have been looking at debugging the memory usage in a forking TCP server. I think I am doing pretty well, I just can't seem to find information on the 'bytes allocated' number in the 'heap summary'. This number seems to be ever increasing the longer my server runs:</p> <pre><code>==27526== ==27526== HEAP SUMMARY: ==27526== in use at exit: 0 bytes in 0 blocks ==27526== total heap usage: 113 allocs, 113 frees, 283,043 bytes allocated ==27526== ==27526== All heap blocks were freed -- no leaks are possible ==27526== ==27526== For counts of detected and suppressed errors, rerun with: -v ==27526== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2) ==27528== ==27528== HEAP SUMMARY: ==27528== in use at exit: 0 bytes in 0 blocks ==27528== total heap usage: 120 allocs, 120 frees, 300,808 bytes allocated ==27528== ==27528== All heap blocks were freed -- no leaks are possible ==27528== ==27528== For counts of detected and suppressed errors, rerun with: -v ==27528== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2) ==27537== ==27537== HEAP SUMMARY: ==27537== in use at exit: 0 bytes in 0 blocks ==27537== total heap usage: 127 allocs, 127 frees, 318,573 bytes allocated ==27537== ==27537== All heap blocks were freed -- no leaks are possible ==27537== ==27537== For counts of detected and suppressed errors, rerun with: -v ==27537== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2) </code></pre> <p>Although Valgrind reports allocs and free are equal and no leaks are possible I do not trust the allocated bytes increasing. </p> <p>So : if the bytes allocated keeps increasing does this mean I have to deallocate from the heap somewhere even if Valgrind reports no leaks are possible?</p> <p>Thanks!</p> <p>EDIT: With Gordon Bailey's answer and the other tips I am still a bit weary. Wrote this little app:</p> <pre><code>/* client.c */ #include &lt;stdio.h&gt; void child_func(int childnum); int main(int argc, char *argv[]) { int nchildren = 1; int pid; int x; if (argc &gt; 1) { nchildren = atoi(argv[1]); } for (x = 0; x &lt; nchildren; x++) { if ((pid = fork()) == 0) { child_func(x + 1); exit(0); } } wait(NULL); return 0; } void child_func(int childnum) { int i; for (i = 0; i &lt; 1000; i++) { free(malloc(1)); } sleep(1); } </code></pre> <p>When I run this the Valgrind output is:</p> <pre><code>==28245== HEAP SUMMARY: ==28245== in use at exit: 0 bytes in 0 blocks ==28245== total heap usage: 1,000 allocs, 1,000 frees, 1,000 bytes allocated ==28245== ==28245== All heap blocks were freed -- no leaks are possible ==28245== ==28245== For counts of detected and suppressed errors, rerun with: -v ==28245== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2) ==28246== HEAP SUMMARY: ==28246== in use at exit: 0 bytes in 0 blocks ==28246== total heap usage: 1,000 allocs, 1,000 frees, 1,000 bytes allocated ==28246== ==28246== All heap blocks were freed -- no leaks are possible </code></pre> <p>So it looks like all memory is cleared on the heap and is definitely different from the output of my app.</p>
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    1. CODo you have something in your server that is dependent on the history? Are the input to the program deterministic? If so, what happens if you give it the exact same input? Note that, input also consists of all files it opens.
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    2. CONope. The server accepts an incoming connect, forks itself to handle the connect, decodes the data and inserts into a Mysql database. After that I exit the fork and no data needs to be retained. I call exit on the fork, so it should in my opinion clear all data from heap.
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    3. COIt looks like it's just Valgrinds way of reporting total used memory over the course of the lifetime of the app (judging by the two answers below). I have no clue why I would want to know this, but such is life.
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