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/*
 * DAMON api
 *
 * Author: SeongJae Park <sjpark@amazon.de>
 */

#ifndef _DAMON_H_
#define _DAMON_H_

#include <linux/memcontrol.h>
#include <linux/mutex.h>
#include <linux/time64.h>
#include <linux/types.h>
#include <linux/random.h>

/* Minimal region size.  Every damon_region is aligned by this. */
#define DAMON_MIN_REGION	PAGE_SIZE
/* Max priority score for DAMON-based operation schemes */
#define DAMOS_MAX_SCORE		(99)

/* Get a random number in [l, r) */
static inline unsigned long damon_rand(unsigned long l, unsigned long r)
{
	return l + prandom_u32_max(r - l);
}

/**
 * struct damon_addr_range - Represents an address region of [@start, @end).
 * @start:	Start address of the region (inclusive).
 * @end:	End address of the region (exclusive).
 */
struct damon_addr_range {
	unsigned long start;
	unsigned long end;
};

/**
 * struct damon_region - Represents a monitoring target region.
 * @ar:			The address range of the region.
 * @sampling_addr:	Address of the sample for the next access check.
 * @nr_accesses:	Access frequency of this region.
 * @list:		List head for siblings.
 * @age:		Age of this region.
 *
 * @age is initially zero, increased for each aggregation interval, and reset
 * to zero again if the access frequency is significantly changed.  If two
 * regions are merged into a new region, both @nr_accesses and @age of the new
 * region are set as region size-weighted average of those of the two regions.
 */
struct damon_region {
	struct damon_addr_range ar;
	unsigned long sampling_addr;
	unsigned int nr_accesses;
	struct list_head list;

	unsigned int age;
/* private: Internal value for age calculation. */
	unsigned int last_nr_accesses;
};

/**
 * struct damon_target - Represents a monitoring target.
 * @pid:		The PID of the virtual address space to monitor.
 * @nr_regions:		Number of monitoring target regions of this target.
 * @regions_list:	Head of the monitoring target regions of this target.
 * @list:		List head for siblings.
 *
 * Each monitoring context could have multiple targets.  For example, a context
 * for virtual memory address spaces could have multiple target processes.  The
 * @pid should be set for appropriate &struct damon_operations including the
 * virtual address spaces monitoring operations.
 */
struct damon_target {
	struct pid *pid;
	unsigned int nr_regions;
	struct list_head regions_list;
	struct list_head list;
};

/**
 * enum damos_action - Represents an action of a Data Access Monitoring-based
 * Operation Scheme.
 *
 * @DAMOS_WILLNEED:	Call ``madvise()`` for the region with MADV_WILLNEED.
 * @DAMOS_COLD:		Call ``madvise()`` for the region with MADV_COLD.
 * @DAMOS_PAGEOUT:	Call ``madvise()`` for the region with MADV_PAGEOUT.
 * @DAMOS_HUGEPAGE:	Call ``madvise()`` for the region with MADV_HUGEPAGE.
 * @DAMOS_NOHUGEPAGE:	Call ``madvise()`` for the region with MADV_NOHUGEPAGE.
 * @DAMOS_LRU_PRIO:	Prioritize the region on its LRU lists.
 * @DAMOS_LRU_DEPRIO:	Deprioritize the region on its LRU lists.
 * @DAMOS_STAT:		Do nothing but count the stat.
 * @NR_DAMOS_ACTIONS:	Total number of DAMOS actions
 */
enum damos_action {
	DAMOS_WILLNEED,
	DAMOS_COLD,
	DAMOS_PAGEOUT,
	DAMOS_HUGEPAGE,
	DAMOS_NOHUGEPAGE,
	DAMOS_LRU_PRIO,
	DAMOS_LRU_DEPRIO,
	DAMOS_STAT,		/* Do nothing but only record the stat */
	NR_DAMOS_ACTIONS,
};

/**
 * struct damos_quota - Controls the aggressiveness of the given scheme.
 * @ms:			Maximum milliseconds that the scheme can use.
 * @sz:			Maximum bytes of memory that the action can be applied.
 * @reset_interval:	Charge reset interval in milliseconds.
 *
 * @weight_sz:		Weight of the region's size for prioritization.
 * @weight_nr_accesses:	Weight of the region's nr_accesses for prioritization.
 * @weight_age:		Weight of the region's age for prioritization.
 *
 * To avoid consuming too much CPU time or IO resources for applying the
 * &struct damos->action to large memory, DAMON allows users to set time and/or
 * size quotas.  The quotas can be set by writing