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 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * DAMON api
  *
  * Author: SeongJae Park <sjpark@amazon.de>
  */
 
 #ifndef _DAMON_H_
 #define _DAMON_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 non-zero values to &ms and
  * &sz, respectively.  If the time quota is set, DAMON tries to use only up to
  * &ms milliseconds within &reset_interval for applying the action.  If the
  * size quota is set, DAMON tries to apply the action only up to &sz bytes
  * within &reset_interval.
  *
  * Internally, the time quota is transformed to a size quota using estimated
  * throughput of the scheme's action.  DAMON then compares it against &sz and
  * uses smaller one as the effective quota.
  *
  * For selecting regions within the quota, DAMON prioritizes current scheme's
  * target memory regions using the &struct damon_operations->get_scheme_score.
  * You could customize the prioritization logic by setting &weight_sz,
  * &weight_nr_accesses, and &weight_age, because monitoring operations are
  * encouraged to respect those.
  */
 struct damos_quota {
     unsigned long ms;
     unsigned long sz;
     unsigned long reset_interval;
 
     unsigned int weight_sz;
     unsigned int weight_nr_accesses;
     unsigned int weight_age;
 
 /* private: */
     /* For throughput estimation */
     unsigned long total_charged_sz;
     unsigned long total_charged_ns;
 
     unsigned long esz;  /* Effective size quota in bytes */
 
     /* For charging the quota */
     unsigned long charged_sz;
     unsigned long charged_from;
     struct damon_target *charge_target_from;
     unsigned long charge_addr_from;
 
     /* For prioritization */
     unsigned long histogram[DAMOS_MAX_SCORE + 1];
     unsigned int min_score;
 };
 
 /**
  * enum damos_wmark_metric - Represents the watermark metric.
  *
  * @DAMOS_WMARK_NONE:       Ignore the watermarks of the given scheme.
  * @DAMOS_WMARK_FREE_MEM_RATE:  Free memory rate of the system in [0,1000].
  * @NR_DAMOS_WMARK_METRICS: Total number of DAMOS watermark metrics
  */
 enum damos_wmark_metric {
     DAMOS_WMARK_NONE,
     DAMOS_WMARK_FREE_MEM_RATE,
     NR_DAMOS_WMARK_METRICS,
 };
 
 /**
  * struct damos_watermarks - Controls when a given scheme should be activated.
  * @metric: Metric for the watermarks.
  * @interval:   Watermarks check time interval in microseconds.
  * @high:   High watermark.
  * @mid:    Middle watermark.
  * @low:    Low watermark.
  *
  * If &metric is &DAMOS_WMARK_NONE, the scheme is always active.  Being active
  * means DAMON does monitoring and applying the action of the scheme to
  * appropriate memory regions.  Else, DAMON checks &metric of the system for at
  * least every &interval microseconds and works as below.
  *
  * If &metric is higher than &high, the scheme is inactivated.  If &metric is
  * between &mid and &low, the scheme is activated.  If &metric is lower than
  * &low, the scheme is inactivated.
  */
 struct damos_watermarks {
     enum damos_wmark_metric metric;
     unsigned long interval;
     unsigned long high;
     unsigned long mid;
     unsigned long low;
 
 /* private: */
     bool activated;
 };
 
 /**
  * struct damos_stat - Statistics on a given scheme.
  * @nr_tried:   Total number of regions that the scheme is tried to be applied.
  * @sz_tried:   Total size of regions that the scheme is tried to be applied.
  * @nr_applied: Total number of regions that the scheme is applied.
  * @sz_applied: Total size of regions that the scheme is applied.
  * @qt_exceeds: Total number of times the quota of the scheme has exceeded.
  */
 struct damos_stat {
     unsigned long nr_tried;
     unsigned long sz_tried;
     unsigned long nr_applied;
     unsigned long sz_applied;
     unsigned long qt_exceeds;
 };
 
 /**
  * struct damos - Represents a Data Access Monitoring-based Operation Scheme.
  * @min_sz_region:  Minimum size of target regions.
  * @max_sz_region:  Maximum size of target regions.
  * @min_nr_accesses:    Minimum ``->nr_accesses`` of target regions.
  * @max_nr_accesses:    Maximum ``->nr_accesses`` of target regions.
  * @min_age_region: Minimum age of target regions.
  * @max_age_region: Maximum age of target regions.
  * @action:     &damo_action to be applied to the target regions.
  * @quota:      Control the aggressiveness of this scheme.
  * @wmarks:     Watermarks for automated (in)activation of this scheme.
  * @stat:       Statistics of this scheme.
  * @list:       List head for siblings.
  *
  * For each aggregation interval, DAMON finds regions which fit in the
  * condition (&min_sz_region, &max_sz_region, &min_nr_accesses,
  * &max_nr_accesses, &min_age_region, &max_age_region) and applies &action to
  * those.  To avoid consuming too much CPU time or IO resources for the
  * &action, &quota is used.
  *
  * To do the work only when needed, schemes can be activated for specific
  * system situations using &wmarks.  If all schemes that registered to the
  * monitoring context are inactive, DAMON stops monitoring either, and just
  * repeatedly checks the watermarks.
  *
  * If all schemes that registered to a &struct damon_ctx are inactive, DAMON
  * stops monitoring and just repeatedly checks the watermarks.
  *
  * After applying the &action to each region, &stat_count and &stat_sz is
  * updated to reflect the number of regions and total size of regions that the
  * &action is applied.
  */
 struct damos {
     unsigned long min_sz_region;
     unsigned long max_sz_region;
     unsigned int min_nr_accesses;
     unsigned int max_nr_accesses;
     unsigned int min_age_region;
     unsigned int max_age_region;
     enum damos_action action;
     struct damos_quota quota;
     struct damos_watermarks wmarks;
     struct damos_stat stat;
     struct list_head list;
 };
 
 /**
  * enum damon_ops_id - Identifier for each monitoring operations implementation
  *
  * @DAMON_OPS_VADDR:    Monitoring operations for virtual address spaces
  * @DAMON_OPS_FVADDR:   Monitoring operations for only fixed ranges of virtual
  *          address spaces
  * @DAMON_OPS_PADDR:    Monitoring operations for the physical address space
  * @NR_DAMON_OPS:   Number of monitoring operations implementations
  */
 enum damon_ops_id {
     DAMON_OPS_VADDR,
     DAMON_OPS_FVADDR,
     DAMON_OPS_PADDR,
     NR_DAMON_OPS,
 };
 
 struct damon_ctx;
 
 /**
  * struct damon_operations - Monitoring operations for given use cases.
  *
  * @id:             Identifier of this operations set.
  * @init:           Initialize operations-related data structures.
  * @update:         Update operations-related data structures.
  * @prepare_access_checks:  Prepare next access check of target regions.
  * @check_accesses:     Check the accesses to target regions.
  * @reset_aggregated:       Reset aggregated accesses monitoring results.
  * @get_scheme_score:       Get the score of a region for a scheme.
  * @apply_scheme:       Apply a DAMON-based operation scheme.
  * @target_valid:       Determine if the target is valid.
  * @cleanup:            Clean up the context.
  *
  * DAMON can be extended for various address spaces and usages.  For this,
  * users should register the low level operations for their target address
  * space and usecase via the &damon_ctx.ops.  Then, the monitoring thread
  * (&damon_ctx.kdamond) calls @init and @prepare_access_checks before starting
  * the monitoring, @update after each &damon_ctx.ops_update_interval, and
  * @check_accesses, @target_valid and @prepare_access_checks after each
  * &damon_ctx.sample_interval.  Finally, @reset_aggregated is called after each
  * &damon_ctx.aggr_interval.
  *
  * Each &struct damon_operations instance having valid @id can be registered
  * via damon_register_ops() and selected by damon_select_ops() later.
  * @init should initialize operations-related data structures.  For example,
  * this could be used to construct proper monitoring target regions and link
  * those to @damon_ctx.adaptive_targets.
  * @update should update the operations-related data structures.  For example,
  * this could be used to update monitoring target regions for current status.
  * @prepare_access_checks should manipulate the monitoring regions to be
  * prepared for the next access check.
  * @check_accesses should check the accesses to each region that made after the
  * last preparation and update the number of observed accesses of each region.
  * It should also return max number of observed accesses that made as a result
  * of its update.  The value will be used for regions adjustment threshold.
  * @reset_aggregated should reset the access monitoring results that aggregated
  * by @check_accesses.
  * @get_scheme_score should return the priority score of a region for a scheme
  * as an integer in [0, &DAMOS_MAX_SCORE].
  * @apply_scheme is called from @kdamond when a region for user provided
  * DAMON-based operation scheme is found.  It should apply the scheme's action
  * to the region and return bytes of the region that the action is successfully
  * applied.
  * @target_valid should check whether the target is still valid for the
  * monitoring.
  * @cleanup is called from @kdamond just before its termination.
  */
 struct damon_operations {
     enum damon_ops_id id;
     void (*init)(struct damon_ctx *context);
     void (*update)(struct damon_ctx *context);
     void (*prepare_access_checks)(struct damon_ctx *context);
     unsigned int (*check_accesses)(struct damon_ctx *context);
     void (*reset_aggregated)(struct damon_ctx *context);
     int (*get_scheme_score)(struct damon_ctx *context,
             struct damon_target *t, struct damon_region *r,
             struct damos *scheme);
     unsigned long (*apply_scheme)(struct damon_ctx *context,
             struct damon_target *t, struct damon_region *r,
             struct damos *scheme);
     bool (*target_valid)(void *target);
     void (*cleanup)(struct damon_ctx *context);
 };
 
 /**
  * struct damon_callback - Monitoring events notification callbacks.
  *
  * @before_start:   Called before starting the monitoring.
  * @after_wmarks_check: Called after each schemes' watermarks check.
  * @after_sampling: Called after each sampling.
  * @after_aggregation:  Called after each aggregation.
  * @before_terminate:   Called before terminating the monitoring.
  * @private:        User private data.
  *
  * The monitoring thread (&damon_ctx.kdamond) calls @before_start and
  * @before_terminate just before starting and finishing the monitoring,
  * respectively.  Therefore, those are good places for installing and cleaning
  * @private.
  *
  * The monitoring thread calls @after_wmarks_check after each DAMON-based
  * operation schemes' watermarks check.  If users need to make changes to the
  * attributes of the monitoring context while it's deactivated due to the
  * watermarks, this is the good place to do.
  *
  * The monitoring thread calls @after_sampling and @after_aggregation for each
  * of the sampling intervals and aggregation intervals, respectively.
  * Therefore, users can safely access the monitoring results without additional
  * protection.  For the reason, users are recommended to use these callback for
  * the accesses to the results.
  *
  * If any callback returns non-zero, monitoring stops.
  */
 struct damon_callback {
     void *private;
 
     int (*before_start)(struct damon_ctx *context);
     int (*after_wmarks_check)(struct damon_ctx *context);
     int (*after_sampling)(struct damon_ctx *context);
     int (*after_aggregation)(struct damon_ctx *context);
     void (*before_terminate)(struct damon_ctx *context);
 };
 
 /**
  * struct damon_ctx - Represents a context for each monitoring.  This is the
  * main interface that allows users to set the attributes and get the results
  * of the monitoring.
  *
  * @sample_interval:        The time between access samplings.
  * @aggr_interval:      The time between monitor results aggregations.
  * @ops_update_interval:    The time between monitoring operations updates.
  *
  * For each @sample_interval, DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
  * each region) for @aggr_interval time.  DAMON also checks whether the target
  * memory regions need update (e.g., by ``mmap()`` calls from the application,
  * in case of virtual memory monitoring) and applies the changes for each
  * @ops_update_interval.  All time intervals are in micro-seconds.
  * Please refer to &struct damon_operations and &struct damon_callback for more
  * detail.
  *
  * @kdamond:        Kernel thread who does the monitoring.
  * @kdamond_lock:   Mutex for the synchronizations with @kdamond.
  *
  * For each monitoring context, one kernel thread for the monitoring is
  * created.  The pointer to the thread is stored in @kdamond.
  *
  * Once started, the monitoring thread runs until explicitly required to be
  * terminated or every monitoring target is invalid.  The validity of the
  * targets is checked via the &damon_operations.target_valid of @ops.  The
  * termination can also be explicitly requested by calling damon_stop().
  * The thread sets @kdamond to NULL when it terminates. Therefore, users can
  * know whether the monitoring is ongoing or terminated by reading @kdamond.
  * Reads and writes to @kdamond from outside of the monitoring thread must
  * be protected by @kdamond_lock.
  *
  * Note that the monitoring thread protects only @kdamond via @kdamond_lock.
  * Accesses to other fields must be protected by themselves.
  *
  * @ops:    Set of monitoring operations for given use cases.
  * @callback:   Set of callbacks for monitoring events notifications.
  *
  * @min_nr_regions: The minimum number of adaptive monitoring regions.
  * @max_nr_regions: The maximum number of adaptive monitoring regions.
  * @adaptive_targets:   Head of monitoring targets (&damon_target) list.
  * @schemes:        Head of schemes (&damos) list.
  */
 struct damon_ctx {
     unsigned long sample_interval;
     unsigned long aggr_interval;
     unsigned long ops_update_interval;
 
 /* private: internal use only */
     struct timespec64 last_aggregation;
     struct timespec64 last_ops_update;
 
 /* public: */
     struct task_struct *kdamond;
     struct mutex kdamond_lock;
 
     struct damon_operations ops;
     struct damon_callback callback;
 
     unsigned long min_nr_regions;
     unsigned long max_nr_regions;
     struct list_head adaptive_targets;
     struct list_head schemes;
 };
 
 static inline struct damon_region *damon_next_region(struct damon_region *r)
 {
     return container_of(r->list.next, struct damon_region, list);
 }
 
 static inline struct damon_region *damon_prev_region(struct damon_region *r)
 {
     return container_of(r->list.prev, struct damon_region, list);
 }
 
 static inline struct damon_region *damon_last_region(struct damon_target *t)
 {
     return list_last_entry(&t->regions_list, struct damon_region, list);
 }
 
 #define damon_for_each_region(r, t) \
     list_for_each_entry(r, &t->regions_list, list)
 
 #define damon_for_each_region_safe(r, next, t) \
     list_for_each_entry_safe(r, next, &t->regions_list, list)
 
 #define damon_for_each_target(t, ctx) \
     list_for_each_entry(t, &(ctx)->adaptive_targets, list)
 
 #define damon_for_each_target_safe(t, next, ctx)    \
     list_for_each_entry_safe(t, next, &(ctx)->adaptive_targets, list)
 
 #define damon_for_each_scheme(s, ctx) \
     list_for_each_entry(s, &(ctx)->schemes, list)
 
 #define damon_for_each_scheme_safe(s, next, ctx) \
     list_for_each_entry_safe(s, next, &(ctx)->schemes, list)
 
 #ifdef CONFIG_DAMON
 
 struct damon_region *damon_new_region(unsigned long start, unsigned long end);
 
 /*
  * Add a region between two other regions
  */
 static inline void damon_insert_region(struct damon_region *r,
         struct damon_region *prev, struct damon_region *next,
         struct damon_target *t)
 {
     __list_add(&r->list, &prev->list, &next->list);
     t->nr_regions++;
 }
 
 void damon_add_region(struct damon_region *r, struct damon_target *t);
 void damon_destroy_region(struct damon_region *r, struct damon_target *t);
 int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges,
         unsigned int nr_ranges);
 
 struct damos *damon_new_scheme(
         unsigned long min_sz_region, unsigned long max_sz_region,
         unsigned int min_nr_accesses, unsigned int max_nr_accesses,
         unsigned int min_age_region, unsigned int max_age_region,
         enum damos_action action, struct damos_quota *quota,
         struct damos_watermarks *wmarks);
 void damon_add_scheme(struct damon_ctx *ctx, struct damos *s);
 void damon_destroy_scheme(struct damos *s);
 
 struct damon_target *damon_new_target(void);
 void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);
 bool damon_targets_empty(struct damon_ctx *ctx);
 void damon_free_target(struct damon_target *t);
 void damon_destroy_target(struct damon_target *t);
 unsigned int damon_nr_regions(struct damon_target *t);
 
 struct damon_ctx *damon_new_ctx(void);
 void damon_destroy_ctx(struct damon_ctx *ctx);
 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
         unsigned long aggr_int, unsigned long ops_upd_int,
         unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_set_schemes(struct damon_ctx *ctx,
             struct damos **schemes, ssize_t nr_schemes);
 int damon_nr_running_ctxs(void);
 bool damon_is_registered_ops(enum damon_ops_id id);
 int damon_register_ops(struct damon_operations *ops);
 int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id);
 
 static inline bool damon_target_has_pid(const struct damon_ctx *ctx)
 {
     return ctx->ops.id == DAMON_OPS_VADDR || ctx->ops.id == DAMON_OPS_FVADDR;
 }
 
 
 int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive);
 int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
 
 #endif  /* CONFIG_DAMON */
 
 #endif  /* _DAMON_H */

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