xref: /linux/include/linux/flex_proportions.h (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Floating proportions with flexible aging period
 *
 *  Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz>
 */

#ifndef _LINUX_FLEX_PROPORTIONS_H
#define _LINUX_FLEX_PROPORTIONS_H

#include <linux/percpu_counter.h>
#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/gfp.h>

/*
 * When maximum proportion of some event type is specified, this is the
 * precision with which we allow limitting. Note that this creates an upper
 * bound on the number of events per period like
 *   ULLONG_MAX >> FPROP_FRAC_SHIFT.
 */
#define FPROP_FRAC_SHIFT 10
#define FPROP_FRAC_BASE (1UL << FPROP_FRAC_SHIFT)

/*
 * ---- Global proportion definitions ----
 */
struct fprop_global {
	/* Number of events in the current period */
	struct percpu_counter events;
	/* Current period */
	unsigned int period;
	/* Synchronization with period transitions */
	seqcount_t sequence;
};

int fprop_global_init(struct fprop_global *p, gfp_t gfp);
void fprop_global_destroy(struct fprop_global *p);
bool fprop_new_period(struct fprop_global *p, int periods);

/*
 * ---- PERCPU ----
 */
struct fprop_local_percpu {
	/* the local events counter */
	struct percpu_counter events;
	/* Period in which we last updated events */
	unsigned int period;
	raw_spinlock_t lock;	/* Protect period and numerator */
};

int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp);
void fprop_local_destroy_percpu(struct fprop_local_percpu *pl);
void __fprop_add_percpu(struct fprop_global *p, struct fprop_local_percpu *pl,
		long nr);
void __fprop_add_percpu_max(struct fprop_global *p,
		struct fprop_local_percpu *pl, int max_frac, long nr);
void fprop_fraction_percpu(struct fprop_global *p,
	struct fprop_local_percpu *pl, unsigned long *numerator,
	unsigned long *denominator);

static inline
void fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
{
	unsigned long flags;

	local_irq_save(flags);
	__fprop_add_percpu(p, pl, 1);
	local_irq_restore(flags);
}

#endif