How Can I Accurately Monitor C Memory Usage at Runtime?

Memory Usage Monitoring in C during Runtime

Introduction

Obtaining accurate memory usage metrics at runtime is crucial for optimizing performance and debugging memory-related issues. This article explores different approaches to retrieve memory usage information in C applications, primarily focusing on the virtual memory size (VIRT) and resident set size (RES).

Using getrusage() Method

The initial attempt to employ the getrusage() function often results in obtaining zero values, as demonstrated in the provided code snippet. This is primarily because getrusage() retrieves resource usage information from the entire system rather than the specific process.

Alternative Solution: Reading from /proc/pid

On Linux systems, a more reliable approach involves reading information from the /proc/pid directory. Each process has its own dedicated directory where various statistics are maintained.

The following code snippet provides a utility function (process_mem_usage()) that reads the /proc/self/stat file to obtain the process's virtual memory size (vsize) and resident set size (rss):

void process_mem_usage(double& vm_usage, double& resident_set)
{
    ifstream stat_stream("/proc/self/stat", ios_base::in);
    unsigned long vsize;
    long rss;
    stat_stream >> vsize >> rss;
    long page_size_kb = sysconf(_SC_PAGE_SIZE) / 1024;
    vm_usage = vsize / 1024.0;
    resident_set = rss * page_size_kb;
}

Demonstration

The main function calls process_mem_usage() to retrieve the memory usage information and prints it to the console:

int main()
{
    double vm, rss;
    process_mem_usage(vm, rss);
    cout << "VM: " << vm << "; RSS: " << rss << endl;
}

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