little help with memory leak/management by the kernel/libg++/libc?
Jairo Medina
jairo19@interhosting.us
Tue Apr 8 19:23:00 GMT 2008
Hola:
This demo program I wrote shows how much memory the process is using (as
given by the kernel /proc/self/status interface) before and after I
request and free memory.
So the issue is that as I request and free memory of different sizes,
the process seems not to relinquish the full amount of requested memory.
My real world program seems to have a small loss of approx 100Kb for
almost each memory request/release cycle, and it needs to do this 500000
times, so you can imagine that I am running out of memory, but the
program is releasing all the memory it asks for. In both cases valgrind
does not report any leaks.
In the table you see that the demo program starts with 180Kb, but ends
using 556Kb. I do not understand why.
[jairo@linux5 scripts]$ make memfree
g++ memfree.cpp -o memfree
[jairo@linux5 scripts]$ ./memfree
VmStk VmLib VmData VmSize VmRSS
84 2540 *180* 2876 * 832*
84 2540 436 3132 916
84 2540 184 2880 916
84 2540 184 2880 916
84 2540 748 3444 920
84 2540 184 2880 916
84 2540 184 2880 916
84 2540 624 3320 920
84 2540 184 2880 920
84 2540 184 2880 920
84 2540 *1188* 3884 924
84 2540 *184* 2880 *920*
84 2540 184 2880 920
84 2540 556 3252 928
84 2540 556 3252 928
84 2540 556 3252 928
84 2540 *556* 3252 *940*
Program:
memfree.cpp
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
string getProcStatus(char*field) {
string s = "";
ifstream in;
in.open("/proc/self/status");
while(!in.eof()) {
in >> s;
if (s.find(field) == string::npos) continue;
in >> s;
break;
}
in.close();
return(s);
} // getProcStatus
class bar {
public:
int one;
int two;
int three;
double four;
double five;
double six;
double seven;
long long eight;
int nine;
double ten;
};
int main() {
bar *memory_get = NULL;
cout << "Virt mem used before creating data 1: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
memory_get = new bar[4000];
cout << "Virt mem used after creating/before deleting data 1: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
delete[] memory_get;
cout << "Virt mem used after deleting data 1: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
cout << "Virt mem used before creating data 2: "<<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib") <<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
memory_get = new bar[9000];
cout << "Virt mem used after creating/before deleting data 2: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
delete[] memory_get;
cout << "Virt mem used after deleting data 2: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
cout << "Virt mem used before creating data 3: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
memory_get = new bar[7000];
cout << "Virt mem used after creating/before deleting data 3: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
delete[] memory_get;
cout << "Virt mem used after deleting data 3: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
cout << "Virt mem used before creating data 4: "<<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" " <<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
memory_get = new bar[16000];
cout << "Virt mem used after creating/before deleting data 4: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
delete[] memory_get;
cout << "Virt mem used after deleting data 4: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
cout<<endl;
cout << "Virt mem used before creating data 5: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
for(unsigned int i = 0; i < 100000; ++i) {
unsigned int j = 1 + (int) (10.0 * (rand() / (RAND_MAX + 1.0)));
memory_get = new bar[6000*j];
delete[] memory_get;
}
cout << "Virt mem used after deleting data 5: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
sleep(5);
sleep(5);
cout<<endl;
cout << "Virt mem used before creating data 6: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
for(unsigned int i = 0; i < 1000000; ++i) {
unsigned int j = 1 + (int) (10.0 * (rand() / (RAND_MAX + 1.0)));
memory_get = new bar[6000*j];
delete[] memory_get;
}
cout << "Virt mem used after deleting data 6: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
cout << "Virt mem used after deleting data 7: " <<
getProcStatus("VmStk")<<" "<< getProcStatus("VmLib")<<" "<<
getProcStatus("VmData")<<" "<< getProcStatus("VmSize")<<" " <<
getProcStatus("VmRSS")<<" pointer "<<memory_get << endl;
}
NOTE: same program but using malloc/free of a struct instead of
new/delete of a class has the same result, but with a smaller VmRSS in
almost every instance. Also the programs wait for 10 seconds to see if
the kernel needs time adjusting the status.
There seems to be a relationship between the size after the delete if
the next requested block of memory is smaller (the VmData increases), I
modified the program a bit to first allocate 6000, then 5000, then 4000,
then 3000 and the result is:
VmStk VmLib VmData VmSize VmRSS
84 2540 *180* 2880 * 828*
84 2540 *560 * 3260 912
84 2540 184 2884 912
84 2540 184 2884 912
84 2540 *496* 3196 920
84 2540 496 3196 920
84 2540 496 3196 920
84 2540 496 3196 928
84 2540 496 3196 932
84 2540 496 3196 932
84 2540 496 3196 940
84 2540 496 3196 948
84 2540 496 3196 948
84 2540 496 3196 956
84 2540 496 3196 956
84 2540 496 3196 956
84 2540 *496* 3196 *956*
84 2540 *180** 2880 *828**
84 2540 *560** 3260 912
84 2540 184 2884 912
84 2540 184 2884 912
84 2540 *496** 3196 920
84 2540 496 3196 920
84 2540 496 3196 920
84 2540 496 3196 928
84 2540 496 3196 932
84 2540 496 3196 932
84 2540 496 3196 940
84 2540 496 3196 948
84 2540 496 3196 948
84 2540 496 3196 956
84 2540 496 3196 956
84 2540 496 3196 956
84 2540 *496** 3196 *956**
I'm using FC7, and FC8, I also tried it in kubuntu, all with similar
results.
What do you think?
Thanks in advance.
--
Jairo Medina
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