MOHAMED
Reputation: 43518
Get memory overflow caused by a memory leak and the application keep running and allocating
I developed a small application for a memory leak stress:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
int period = 0;
int size = 40000001;
char *buf = NULL;
if (argc > 1) period = atoi(argv[1]);
if (period == 0) period = 21;
for (;;) {
buf = malloc(size);
if (buf == NULL) printf ("malloc return NULL\n");
sleep(period);
}
return 0;
}
the application make a memory allocation (without free) of ~40M every 20 second. my system memory is ~256M.
I checked the memory consumed by the stress application with the top command:
$top | grep "stress"
873 5689 root S 39892 16% 0% ./stress_test
873 5689 root S 39892 16% 0% ./stress_test
873 5689 root S 39892 16% 0% ./stress_test
873 5689 root S 78956 31% 0% ./stress_test
873 5689 root S 78956 31% 0% ./stress_test
873 5689 root S 78956 31% 0% ./stress_test
873 5689 root S 78956 31% 0% ./stress_test
873 5689 root S 78956 31% 0% ./stress_test
873 5689 root S 115m 47% 0% ./stress_test
873 5689 root S 115m 47% 0% ./stress_test
873 5689 root S 115m 47% 0% ./stress_test
873 5689 root S 115m 47% 0% ./stress_test
873 5689 root S 153m 62% 0% ./stress_test
873 5689 root S 153m 62% 0% ./stress_test
873 5689 root S 153m 62% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 153m 62% 0% ./stress_test
873 5689 root S 191m 77% 0% ./stress_test
873 5689 root S 191m 77% 0% ./stress_test
873 5689 root S 191m 77% 0% ./stress_test
873 5689 root S 191m 77% 0% ./stress_test
873 5689 root S 229m 93% 0% ./stress_test
873 5689 root S 229m 93% 0% ./stress_test
873 5689 root S 229m 93% 0% ./stress_test
873 5689 root S 229m 93% 0% ./stress_test
873 5689 root S 267m 108% 0% ./stress_test
873 5689 root S 267m 108% 0% ./stress_test
873 5689 root S 267m 108% 0% ./stress_test
873 5689 root S 267m 108% 0% ./stress_test
873 5689 root S 305m 124% 0% ./stress_test
873 5689 root S 305m 124% 0% ./stress_test
873 5689 root S 305m 124% 0% ./stress_test
873 5689 root S 305m 124% 0% ./stress_test
873 5689 root S 305m 124% 0% ./stress_test
873 5689 root S 344m 139% 0% ./stress_test
873 5689 root S 344m 139% 0% ./stress_test
873 5689 root S 344m 139% 0% ./stress_test
873 5689 root S 344m 139% 0% ./stress_test
873 5689 root S 382m 155% 0% ./stress_test
873 5689 root S 382m 155% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 382m 155% 0% ./stress_test
873 5689 root S 382m 155% 0% ./stress_test
873 5689 root S 420m 170% 0% ./stress_test
873 5689 root S 420m 170% 0% ./stress_test
873 5689 root S 420m 170% 0% ./stress_test
873 5689 root S 458m 185% 0% ./stress_test
873 5689 root S 458m 185% 0% ./stress_test
873 5689 root S 458m 185% 0% ./stress_test
873 5689 root S 458m 185% 0% ./stress_test
873 5689 root S 496m 201% 0% ./stress_test
873 5689 root S 496m 201% 0% ./stress_test
873 5689 root S 496m 201% 0% ./stress_test
873 5689 root S 496m 201% 0% ./stress_test
873 5689 root S 534m 216% 0% ./stress_test
873 5689 root S 534m 216% 0% ./stress_test
873 5689 root S 534m 216% 0% ./stress_test
873 5689 root S 534m 216% 0% ./stress_test
873 5689 root S 534m 216% 0% ./stress_test
873 5689 root S 573m 232% 0% ./stress_test
873 5689 root S 573m 232% 0% ./stress_test
873 5689 root S 573m 232% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 573m 232% 0% ./stress_test
873 5689 root S 611m 247% 0% ./stress_test
873 5689 root S 611m 247% 0% ./stress_test
873 5689 root S 611m 247% 0% ./stress_test
873 5689 root S 611m 247% 0% ./stress_test
873 5689 root S 649m 263% 0% ./stress_test
873 5689 root S 649m 263% 0% ./stress_test
873 5689 root S 649m 263% 0% ./stress_test
873 5689 root S 649m 263% 0% ./stress_test
873 5689 root S 687m 278% 0% ./stress_test
873 5689 root S 687m 278% 0% ./stress_test
873 5689 root S 687m 278% 0% ./stress_test
873 5689 root S 687m 278% 0% ./stress_test
873 5689 root S 725m 293% 0% ./stress_test
873 5689 root S 725m 293% 0% ./stress_test
873 5689 root S 725m 293% 0% ./stress_test
873 5689 root S 725m 293% 0% ./stress_test
873 5689 root S 763m 309% 0% ./stress_test
873 5689 root S 763m 309% 0% ./stress_test
873 5689 root S 763m 309% 0% ./stress_test
873 5689 root S 763m 309% 0% ./stress_test
873 5689 root S 763m 309% 0% ./stress_test
873 5689 root S 801m 324% 0% ./stress_test
873 5689 root S 801m 324% 0% ./stress_test
873 5689 root S 801m 324% 0% ./stress_test
873 5689 root S 801m 324% 0% ./stress_test
873 5689 root S 840m 340% 0% ./stress_test
873 5689 root S 840m 340% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 840m 340% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 840m 340% 0% ./stress_test
Mem: 120004K used, 132592K free, 0K shrd, 0K buff, 30076K cached
873 5689 root S 878m 355% 0% ./stress_test
873 5689 root S 878m 355% 0% ./stress_test
873 5689 root S 878m 355% 0% ./stress_test
873 5689 root S 878m 355% 0% ./stress_test
873 5689 root S 916m 370% 0% ./stress_test
873 5689 root S 916m 370% 0% ./stress_test
873 5689 root S 916m 370% 0% ./stress_test
873 5689 root S 916m 370% 0% ./stress_test
873 5689 root S 954m 386% 0% ./stress_test
873 5689 root S 954m 386% 0% ./stress_test
873 5689 root S 954m 386% 0% ./stress_test
873 5689 root S 954m 386% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 992m 401% 0% ./stress_test
873 5689 root S 992m 401% 0% ./stress_test
873 5689 root S 992m 401% 0% ./stress_test
873 5689 root S 992m 401% 0% ./stress_test
873 5689 root S 992m 401% 0% ./stress_test
873 5689 root S 1030m 417% 0% ./stress_test
873 5689 root S 1030m 417% 0% ./stress_test
873 5689 root S 1030m 417% 0% ./stress_test
873 5689 root S 1030m 417% 0% ./stress_test
873 5689 root S 1068m 432% 0% ./stress_test
873 5689 root S 1068m 432% 0% ./stress_test
873 5689 root S 1068m 432% 0% ./stress_test
873 5689 root S 1068m 432% 0% ./stress_test
873 5689 root S 1107m 448% 0% ./stress_test
873 5689 root S 1107m 448% 0% ./stress_test
873 5689 root S 1107m 448% 0% ./stress_test
873 5689 root S 1107m 448% 0% ./stress_test
873 5689 root S 1145m 463% 0% ./stress_test
873 5689 root S 1145m 463% 0% ./stress_test
873 5689 root S 1145m 463% 0% ./stress_test
873 5689 root S 1145m 463% 0% ./stress_test
873 5689 root S 1183m 478% 0% ./stress_test
873 5689 root S 1183m 478% 0% ./stress_test
873 5689 root S 1183m 478% 0% ./stress_test
873 5689 root S 1183m 478% 0% ./stress_test
873 5689 root S 1221m 494% 0% ./stress_test
873 5689 root S 1221m 494% 0% ./stress_test
873 5689 root S 1221m 494% 0% ./stress_test
873 5689 root S 1221m 494% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1221m 494% 0% ./stress_test
873 5689 root S 1259m 509% 0% ./stress_test
873 5689 root S 1259m 509% 0% ./stress_test
873 5689 root S 1259m 509% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1259m 509% 0% ./stress_test
873 5689 root S 1297m 525% 0% ./stress_test
873 5689 root S 1297m 525% 0% ./stress_test
873 5689 root S 1297m 525% 0% ./stress_test
873 5689 root S 1297m 525% 0% ./stress_test
873 5689 root S 1336m 540% 0% ./stress_test
873 5689 root S 1336m 540% 0% ./stress_test
873 5689 root S 1336m 540% 0% ./stress_test
873 5689 root S 1336m 540% 0% ./stress_test
873 5689 root S 1374m 556% 0% ./stress_test
873 5689 root S 1374m 556% 0% ./stress_test
873 5689 root S 1374m 556% 0% ./stress_test
873 5689 root S 1374m 556% 0% ./stress_test
873 5689 root S 1412m 571% 0% ./stress_test
873 5689 root S 1412m 571% 0% ./stress_test
873 5689 root S 1412m 571% 0% ./stress_test
873 5689 root S 1412m 571% 0% ./stress_test
873 5689 root S 1450m 586% 0% ./stress_test
873 5689 root S 1450m 586% 0% ./stress_test
873 5689 root S 1450m 586% 0% ./stress_test
873 5689 root S 1450m 586% 0% ./stress_test
873 5689 root S 1450m 586% 0% ./stress_test
873 5689 root S 1488m 602% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1488m 602% 0% ./stress_test
873 5689 root S 1488m 602% 0% ./stress_test
873 5689 root S 1488m 602% 0% ./stress_test
873 5689 root S 1526m 617% 0% ./stress_test
873 5689 root S 1526m 617% 0% ./stress_test
873 5689 root S 1526m 617% 0% ./stress_test
873 5689 root S 1526m 617% 0% ./stress_test
873 5689 root S 1564m 633% 0% ./stress_test
873 5689 root S 1564m 633% 0% ./stress_test
873 5689 root S 1564m 633% 0% ./stress_test
873 5689 root S 1564m 633% 0% ./stress_test
873 5689 root S 1603m 648% 0% ./stress_test
873 5689 root S 1603m 648% 0% ./stress_test
873 5689 root S 1603m 648% 0% ./stress_test
873 5689 root S 1603m 648% 0% ./stress_test
873 5689 root S 1641m 664% 0% ./stress_test
873 5689 root S 1641m 664% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1641m 664% 0% ./stress_test
873 5689 root S 1641m 664% 0% ./stress_test
873 5689 root S 1679m 679% 0% ./stress_test
873 5689 root S 1679m 679% 0% ./stress_test
873 5689 root S 1679m 679% 0% ./stress_test
873 5689 root S 1679m 679% 0% ./stress_test
873 5689 root S 1679m 679% 0% ./stress_test
873 5689 root S 1717m 694% 0% ./stress_test
873 5689 root S 1717m 694% 0% ./stress_test
873 5689 root S 1717m 694% 0% ./stress_test
873 5689 root S 1717m 694% 0% ./stress_test
873 5689 root S 1755m 710% 0% ./stress_test
873 5689 root S 1755m 710% 0% ./stress_test
873 5689 root S 1755m 710% 0% ./stress_test
873 5689 root S 1755m 710% 0% ./stress_test
873 5689 root S 1793m 725% 0% ./stress_test
873 5689 root S 1793m 725% 0% ./stress_test
873 5689 root S 1793m 725% 0% ./stress_test
873 5689 root S 1793m 725% 0% ./stress_test
873 5689 root S 1831m 741% 0% ./stress_test
873 5689 root S 1831m 741% 0% ./stress_test
873 5689 root S 1831m 741% 0% ./stress_test
873 5689 root S 1831m 741% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1870m 756% 0% ./stress_test
873 5689 root S 1870m 756% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1870m 756% 0% ./stress_test
873 5689 root S 1870m 756% 0% ./stress_test
873 5689 root S 1870m 756% 0% ./stress_test
873 5689 root S 1908m 771% 0% ./stress_test
873 5689 root S 1908m 771% 0% ./stress_test
873 5689 root S 1908m 771% 0% ./stress_test
873 5689 root S 1908m 771% 0% ./stress_test
873 5689 root S 1946m 787% 0% ./stress_test
873 5689 root S 1946m 787% 0% ./stress_test
873 5689 root S 1946m 787% 0% ./stress_test
873 5689 root S 1946m 787% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
1061 5689 root S 1564 1% 0% grep stress
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
873 5689 root S 1984m 802% 0% ./stress_test
the forth column is the memory consumed by the application and the 5th column is the memory consumed by the application in percent
So the stress application growth in the memory usage and reach values bigger than the memory size: 1984M (802 % of the memory) and the application keep running and allocating whenthe consumed memory is > 100%. But it stops allocating and keep running when it reachs
28308 5682 root S 2022m 818% 0% ./stress_test
I expected that my application stop allocating when it reached 100%.
Could you explain this behaviour?
Upvotes: 0
Views: 120
Answers (2)
Rakib
Reputation: 7625
Crash will happen when you try to use memory after when allocation actually fails. (other reasons include dereferencing wild pointer, trying to access memory that belongs to other process etc.) but if allocation fails due to unavailability of memory, that alone will not result in crash.
Upvotes: 0
unwind
Reputation: 399813
Why would you expect it to "crash"? If it fails to allocate, malloc() just returns NULL.
Also, note that many modern operating systems (like Linux) typically overcommit the memory, and since your code never actually uses the allocated memory, it can probably do so by a great deal before running out of virtual space and forcing malloc() to fail. This is likely why you see your program using more RAM than is available.
Of course, you failed to say how much swap you have, which will also affect what happens since even if you particular OS doesn't overcommit, it very likely uses swap.
Upvotes: 4
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