Is there a portable way to detect (programmatically) the memory page size using C or C++ code ?
C doesn't know anything about memory pages. On posix systems you can use long pagesize = sysconf(_SC_PAGE_SIZE);
Yes, this is platform-specific. On Linux there's sysconf(_SC_PAGESIZE)
, which also seems to be POSIX. A typical C library implements this using the auxiliary vector. If for some reason you don't have a C library or the auxiliary vector you could determine the page size like this:
size_t get_page_size(void)
{
size_t n;
char *p;
int u;
for (n = 1; n; n *= 2) {
p = mmap(0, n * 2, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
return -1;
u = munmap(p + n, n);
munmap(p, n * 2);
if (!u)
return n;
}
return -1;
}
That's also POSIX, I think. It relies on there being some free memory, but it only needs two consecutive pages. It might be useful in some (weird) circumstances.
Across operating systems, no.
On Linux systems:
#include <unistd.h>
long sz = sysconf (_SC_PAGESIZE);
Since Boost is a pretty portable library you could use mapped_region::get_page_size() function to retrieve the memory page size.
As for C++ Standard it gives no such a possibility.
I think this function helps.
[DllImport("kernel32.dll")]
public static extern void GetSystemInfo([MarshalAs(UnmanagedType.Struct)] ref SYSTEM_INFO lpSystemInfo);
It is entirely platform dependent which address-ranges are mapped to which page-sizes. Further the pagesize is not system-wide. You can allocate memory from different page-size regions according to the use case. And you can even have platforms without any virtual memory managment.
So, code handling this topic must be platform specific.