Source to osfmk/kern/mach_factor.c

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 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
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/*
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/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  [email protected]
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *	File:	kern/mach_factor.c
 *	Author:	Avadis Tevanian, Jr.
 *	Date:	1986
 *
 *	Compute the Mach Factor.
 */

#include <cpus.h>

#include <mach/machine.h>
#include <mach/processor_info.h>
#include <kern/sched.h>
#include <kern/assert.h>
#include <kern/processor.h>
#include <kern/thread.h>
#if	MACH_KERNEL
#include <mach/kern_return.h>
#include <mach/port.h>
#endif	/* MACH_KERNEL */

integer_t	avenrun[3] = {0, 0, 0};
integer_t	mach_factor[3] = {0, 0, 0};

/*
 * Values are scaled by LOAD_SCALE, defined in processor_info.h
 */
static	long	fract[3] = {
	800,			/* (4.0/5.0) 5 second average */
	966,			/* (29.0/30.0) 30 second average */
	983,			/* (59.0/60.) 1 minute average */
};

void
compute_mach_factor(void)
{
	register processor_set_t	pset;
	register processor_t		processor;
	register int				ncpus;
	register int				nthreads;
	register long				factor_now;
	register long				average_now;
	register long				load_now;

	mutex_lock(&all_psets_lock);
	pset = (processor_set_t) queue_first(&all_psets);
	while (!queue_end(&all_psets, (queue_entry_t)pset)) {
	    /*
	     *	If no processors, this pset is in suspended animation.
	     *	No load calculations are performed.
	     */
	    pset_lock(pset);
	    if ((ncpus = pset->processor_count) > 0) {
			/*
			 *	Count number of threads.
			 */
			nthreads = pset->runq.count - pset->runq.depress_count;
#if	NCPUS > 1
			processor = (processor_t)queue_first(&pset->processors);
			while (!queue_end(&pset->processors, (queue_entry_t)processor)) {
				nthreads += processor->runq.count -
									processor->runq.depress_count;
				processor = (processor_t)queue_next(&processor->processors);
		}
#endif

			/*
			 * account for threads on cpus.
			 */
			nthreads += ncpus - pset->idle_count; 

			/*
			 *	The current thread (running this calculation)
			 *	doesn't count; it's always in the default pset.
			 */
			if (pset == &default_pset)
				nthreads -= 1;

			if (nthreads >= ncpus) {
				factor_now = (ncpus * LOAD_SCALE) / (nthreads + 1);
				load_now = (nthreads << SCHED_SHIFT) / ncpus;
			}
			else {
				factor_now = (ncpus - nthreads) * LOAD_SCALE;
				load_now = SCHED_SCALE;
			}

			/*
			 *	Load average and mach factor calculations for
			 *	those that ask about these things.
			 */

			average_now = (nthreads * LOAD_SCALE) / ncpus;

			pset->mach_factor =	((pset->mach_factor << 2) + factor_now) / 5;
			pset->load_average = ((pset->load_average << 2) + average_now) / 5;

			/*
			 *	And some ugly stuff to keep w happy.
			 */
			if (pset == &default_pset) {
				register int i;

				for (i = 0; i < 3; i++) {
					mach_factor[i] = ((mach_factor[i] * fract[i]) +
						(factor_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;

					avenrun[i] = ((avenrun[i] * fract[i]) +
						(average_now * (LOAD_SCALE - fract[i]))) / LOAD_SCALE;
				}
			}

			/*
			 *	sched_load is the only thing used by scheduler.
			 *	It is always at least 1 (i.e. SCHED_SCALE).
			 */
			pset->sched_load = (pset->sched_load + load_now) >> 1;
	    }

	    pset_unlock(pset);
	    pset = (processor_set_t) queue_next(&pset->all_psets);
	}

	mutex_unlock(&all_psets_lock);
}