// gcc -fPIC -shared sysconf-caching.c -ldl  -o sysconf-caching.so
#define _GNU_SOURCE 1
#include <dlfcn.h>
#include <sched.h>
#include <unistd.h>

static long int (*real_sysconf)(int name);

long int sysconf(int name)
{
	if (!real_sysconf) 
		real_sysconf = dlsym(RTLD_NEXT, "sysconf");

	if (name == _SC_NPROCESSORS_ONLN) {
		static int cache = -1; 

		if (cache == -1)
			cache = real_sysconf( _SC_NPROCESSORS_ONLN);
		return cache;
	}

	return real_sysconf(name);
}