xnu-1228.tar.gz

[apple/xnu.git] / osfmk / kern / sched_average.c

/*
 * Copyright (c) 2000-2007 Apple Computer, Inc. All rights reserved.
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 * Version 2.0 (the 'License'). You may not use this file except in
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 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
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/*
 * @OSF_COPYRIGHT@
 */
/* 
 * 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  Software.Distribution@CS.CMU.EDU
 *  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.
 */
/*
 */
/*
 *	Author:	Avadis Tevanian, Jr.
 *	Date:	1986
 *
 *	Compute various averages.
 */

#include <mach/mach_types.h>

#include <kern/sched.h>
#include <kern/assert.h>
#include <kern/processor.h>
#include <kern/thread.h>
	
uint32_t	avenrun[3] = {0, 0, 0};
uint32_t	mach_factor[3] = {0, 0, 0};

/*
 * Values are scaled by LOAD_SCALE, defined in processor_info.h
 */
#define base(n)		((n) << SCHED_TICK_SHIFT)
#define frac(n)		(((base(n) - 1) * LOAD_SCALE) /	base(n))

static uint32_t		fract[3] = {
	frac(5),		/* 5 second average */
	frac(30),		/* 30 second average */
	frac(60),		/* 1 minute average */
};

#undef base
#undef frac

static unsigned int		sched_nrun;

typedef void	(*sched_avg_comp_t)(
					void			*param);

#define SCHED_AVG_SECS(n)	((n) << SCHED_TICK_SHIFT)

static struct sched_average {
	sched_avg_comp_t	comp;
	void				*param;
	int					period;
	int					tick;			
} sched_average[] = {
	{ compute_averunnable, &sched_nrun, SCHED_AVG_SECS(5), 0 },
	{ compute_stack_target, NULL, SCHED_AVG_SECS(5), 1 },
	{ NULL, NULL, 0, 0 }
};

typedef struct sched_average	*sched_average_t;

void
compute_averages(void)
{
	int					ncpus, nthreads, nshared;
	uint32_t			factor_now, average_now, load_now = 0;
	sched_average_t		avg;

	/*
	 *	Retrieve counts, ignoring
	 *	the current thread.
	 */
	ncpus = processor_avail_count;
	nthreads = sched_run_count - 1;
	nshared = sched_share_count;

	/*
	 *	Load average and mach factor calculations for
	 *	those which ask about these things.
	 */
	average_now = nthreads * LOAD_SCALE;

	if (nthreads > ncpus)
		factor_now = (ncpus * LOAD_SCALE) / (nthreads + 1);
	else
		factor_now = (ncpus - nthreads) * LOAD_SCALE;

	sched_mach_factor =	((sched_mach_factor << 2) + factor_now) / 5;
	sched_load_average = ((sched_load_average << 2) + average_now) / 5;

	/*
	 *	Compute the timeshare priority
	 *	conversion factor based on loading.
	 */
	if (nshared > nthreads)
		nshared = nthreads;

	if (nshared > ncpus) {
		if (ncpus > 1)
			load_now = nshared / ncpus;
		else
			load_now = nshared;

		if (load_now > NRQS - 1)
			load_now = NRQS - 1;
	}

	/*
	 *	The conversion factor consists of
	 *	two components: a fixed value based
	 *	on the absolute time unit, and a
	 *	dynamic portion based on loading.
	 *
	 *	Zero loading results in a out of range
	 *	shift count.  Accumulated usage is ignored
	 *	during conversion and new usage deltas
	 *	are discarded.
	 */
	sched_pri_shift = sched_fixed_shift - sched_load_shifts[load_now];

	/*
	 *	Sample total running threads.
	 */
	sched_nrun = nthreads;

	/*
	 * Compute old-style Mach load averages.
	 */
	{
		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;
		}
	}

	/*
	 *	Compute averages in other components.
	 */
	for (avg = sched_average; avg->comp != NULL; ++avg) {
		if (++avg->tick >= avg->period) {
			(*avg->comp)(avg->param);
			avg->tick = 0;
		}
	}
}