Is it possible, for a c++ program, to track how much memory the program is using at one time?
For example, a function with a prototype:
int getEstimatedTotalMemoryUsage();
I suppose if it's not possible, then one will have to get out of the program, do a system call and check the results from there. If so, what tools are available for such purposes? Assuming such a thing is possible, that is.
edit: I'm using linux, any tools that can do this for you?
Yes - use POSIX getrusage. From the Linux man page:
Synopsis
#include <sys/time.h> #include <sys/resource.h> int getrusage(int who, struct rusage *usage);Description
getrusage()returns current resource usages, for a who of eitherRUSAGE_SELForRUSAGE_CHILDREN. The former asks for resources used by the current process, the latter for resources used by those of its children that have terminated and have been waited for.struct rusage { struct timeval ru_utime; /* user time used */ struct timeval ru_stime; /* system time used */ long ru_maxrss; /* maximum resident set size */ long ru_ixrss; /* integral shared memory size */ long ru_idrss; /* integral unshared data size */ long ru_isrss; /* integral unshared stack size */ long ru_minflt; /* page reclaims */ long ru_majflt; /* page faults */ long ru_nswap; /* swaps */ long ru_inblock; /* block input operations */ long ru_oublock; /* block output operations */ long ru_msgsnd; /* messages sent */ long ru_msgrcv; /* messages received */ long ru_nsignals; /* signals received */ long ru_nvcsw; /* voluntary context switches */ long ru_nivcsw; /* involuntary context switches */ };
Here is an example of measuring memory used by process on Windows.
#include <windows.h>
#include <Psapi.h>
// [...]
PROCESS_MEMORY_COUNTERS memCounter;
BOOL result = K32GetProcessMemoryInfo(GetCurrentProcess(), &memCounter, sizeof(memCounter));
std::cout << "WorkingSetSize " << memCounter.WorkingSetSize << std::endl;
And explanations of returned values https://learn.microsoft.com/en-gb/windows/win32/api/psapi/ns-psapi-process_memory_counters
I wanted this today, myself, so sharing the tested results here. I believe a call to getmem() will do what the OP asked, on any unix box. Written in very generic C, it will work in C or C++.
// Calling function must free the returned result.
char* exec(const char* command) {
FILE* fp;
char* line = NULL;
// Following initialization is equivalent to char* result = ""; and just
// initializes result to an empty string, only it works with
// -Werror=write-strings and is so much less clear.
char* result = (char*) calloc(1, 1);
size_t len = 0;
fflush(NULL);
fp = popen(command, "r");
if (fp == NULL) {
printf("Cannot execute command:\n%s\n", command);
return NULL;
}
while(getline(&line, &len, fp) != -1) {
// +1 below to allow room for null terminator.
result = (char*) realloc(result, strlen(result) + strlen(line) + 1);
// +1 below so we copy the final null terminator.
strncpy(result + strlen(result), line, strlen(line) + 1);
free(line);
line = NULL;
}
fflush(fp);
if (pclose(fp) != 0) {
perror("Cannot close stream.\n");
}
return result;
}
int getmem() {
pid_t pid = getpid();
char cmd[64];
snprintf(cmd, 64, "/bin/ps -p %d -o size", pid);
char* result = exec(cmd);
if (!result) {
return 0;
}
// Find first newline.
int pos = 0;
while (result[pos] != '\n') {
pos++;
}
// Remove the final newline.
result[strlen(result) - 1] = '\0';
// Convert to integer.
int size = atoi(result + pos + 1);
free(result);
return size;
}
Technically, I suppose the printf(...) line should be fprintf(stderr, ...), but I tend to have stderr redirected for certain environment-specific logging reasons, and this is how I compiled and tested the code, so I'm copying verbatim to avoid breakage.
Get your PID: pid_t getpid(void); // unistd.h
Parse /proc/<id>/smaps
If you don't care about shared libraries in mem total it may be simpler
make a system call to ps -p <id> -o %mem
