Get Page Size using C

In systems programming, retrieving the memory page size can be important for tasks such as optimizing allocations, aligning buffers, or interacting with low-level APIs. A memory page represents the smallest block of memory managed by the operating system, and its size can vary depending on the platform and architecture. Most systems use 4096 bytes (4 KB) pages, although some environments may use larger values such as 16 KB or 64 KB.

C does not define a standard function for obtaining the page size directly, but operating systems provide their own mechanisms. On Unix-like systems (e.g. Linux), the sysconf function can be used to query runtime configuration values, including the page size. On Windows, similar information is available through system APIs.

The following example demonstrates a cross-platform approach for determining the page size:

#include <stdio.h>

#ifdef _WIN32
#include <windows.h>

long long get_page_size() {
    SYSTEM_INFO sysInfo;
    GetSystemInfo(&sysInfo);

    return (long long) sysInfo.dwPageSize;
}
#else
#include <unistd.h>

long long get_page_size() {
    return sysconf(_SC_PAGE_SIZE);
}
#endif

int main() {
    long long page_size = get_page_size();
    printf("%lld\n", page_size);

    return 0;
}

This program defines a function that abstracts platform-specific details. On Windows systems, GetSystemInfo fills a structure containing various system parameters, including the page size. On Unix-like systems, sysconf is called with _SC_PAGE_SIZE to retrieve the same information.

The function returns the size of one memory page expressed in bytes. On the majority of systems, this value is typically 4096.