Function init_param2

freebsd/kern/subr_param.c:245–330

* Boot time overrides that are scaled against main memory */

 * Boot time overrides that are scaled against main memory
 */
void
init_param2(long physpages)
{

	/* Base parameters */
	maxusers = MAXUSERS;
	TUNABLE_INT_FETCH("kern.maxusers", &maxusers);
	if (maxusers == 0) {
		maxusers = physpages / (2 * 1024 * 1024 / PAGE_SIZE);
		if (maxusers < 32)
			maxusers = 32;
#ifdef VM_MAX_AUTOTUNE_MAXUSERS
                if (maxusers > VM_MAX_AUTOTUNE_MAXUSERS)
                        maxusers = VM_MAX_AUTOTUNE_MAXUSERS;
#endif
                /*
                 * Scales down the function in which maxusers grows once
                 * we hit 384.
                 */
                if (maxusers > 384)
                        maxusers = 384 + ((maxusers - 384) / 8);
        }

	/*
	 * The following can be overridden after boot via sysctl.  Note:
	 * unless overriden, these macros are ultimately based on maxusers.
	 * Limit maxproc so that kmap entries cannot be exhausted by
	 * processes.
	 */
	maxproc = NPROC;
	TUNABLE_INT_FETCH("kern.maxproc", &maxproc);
	if (maxproc > (physpages / 12))
		maxproc = physpages / 12;
	if (maxproc > pid_max)
		maxproc = pid_max;
	maxprocperuid = (maxproc * 9) / 10;

	/*
	 * The default limit for maxfiles is 1/12 of the number of
	 * physical page but not less than 16 times maxusers.
	 * At most it can be 1/6 the number of physical pages.
	 */
	maxfiles = imax(MAXFILES, physpages / 8);
	TUNABLE_INT_FETCH("kern.maxfiles", &maxfiles);
	if (maxfiles > (physpages / 4))
		maxfiles = physpages / 4;
	maxfilesperproc = (maxfiles / 10) * 9;
	TUNABLE_INT_FETCH("kern.maxfilesperproc", &maxfilesperproc);

	/*
	 * Cannot be changed after boot.
	 */
	nbuf = NBUF;
	TUNABLE_INT_FETCH("kern.nbuf", &nbuf);
	TUNABLE_INT_FETCH("kern.bio_transient_maxcnt", &bio_transient_maxcnt);
	maxphys = MAXPHYS;
	TUNABLE_ULONG_FETCH("kern.maxphys", &maxphys);
	if (maxphys == 0) {