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/* SPDX-License-Identifier: GPL-2.0 */
* DAMON api
* Author: SeongJae Park <>
#ifndef _DAMON_H_
#define _DAMON_H_
#include <linux/mutex.h>
#include <linux/time64.h>
#include <linux/types.h>
/* Minimal region size. Every damon_region is aligned by this. */
/* Max priority score for DAMON-based operation schemes */
#define DAMOS_MAX_SCORE (99)
* 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.
* @id: Unique identifier for this target.
* @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
* @id of each target should be unique among the targets of the context. For
* example, in the virtual address monitoring context, it could be a pidfd or
* an address of an mm_struct.
struct damon_target {
unsigned long id;
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_STAT: Do nothing but count the stat.
enum damos_action {
DAMOS_STAT, /* Do nothing but only record the stat */
* 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_primitive->get_scheme_score.
* You could customize the prioritization logic by setting &weight_sz,
* &weight_nr_accesses, and &weight_age, because monitoring primitives 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].
enum damos_wmark_metric {
* 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 - 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_count: Total number of regions that this scheme is applied.
* @stat_sz: Total size of regions that this scheme is applied.
* @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;
unsigned long stat_count;
unsigned long stat_sz;
struct list_head list;
struct damon_ctx;
* struct damon_primitive - Monitoring primitives for given use cases.
* @init: Initialize primitive-internal data structures.
* @update: Update primitive-internal 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 primitives for their target address
* space and usecase via the &damon_ctx.primitive. Then, the monitoring thread
* (&damon_ctx.kdamond) calls @init and @prepare_access_checks before starting
* the monitoring, @update after each &damon_ctx.primitive_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.
* @init should initialize primitive-internal 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 primitive-internal 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. This is not used for &DAMON_ARBITRARY_TARGET case.
* @target_valid should check whether the target is still valid for the
* monitoring.
* @cleanup is called from @kdamond just before its termination.
struct damon_primitive {
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);
int (*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_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_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_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.
* @primitive_update_interval: The time between monitoring primitive 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
* @primitive_update_interval. All time intervals are in micro-seconds.
* Please refer to &struct damon_primitive and &struct damon_callback for more
* detail.
* @kdamond: Kernel thread who does the monitoring.
* @kdamond_stop: Notifies whether kdamond should stop.
* @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_primitive.target_valid of @primitive. The
* termination can also be explicitly requested by writing non-zero to
* @kdamond_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 and @kdamond_stop from
* outside of the monitoring thread must be protected by @kdamond_lock.
* Note that the monitoring thread protects only @kdamond and @kdamond_stop via
* @kdamond_lock. Accesses to other fields must be protected by themselves.
* @primitive: Set of monitoring primitives 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 primitive_update_interval;
/* private: internal use only */
struct timespec64 last_aggregation;
struct timespec64 last_primitive_update;
/* public: */
struct task_struct *kdamond;
struct mutex kdamond_lock;
struct damon_primitive primitive;
struct damon_callback callback;
unsigned long min_nr_regions;
unsigned long max_nr_regions;
struct list_head adaptive_targets;
struct list_head schemes;
#define damon_next_region(r) \
(container_of(r->, struct damon_region, list))
#define damon_prev_region(r) \
(container_of(r->list.prev, struct damon_region, list))
#define damon_last_region(t) \
(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)
struct damon_region *damon_new_region(unsigned long start, unsigned long end);
inline void damon_insert_region(struct damon_region *r,
struct damon_region *prev, struct damon_region *next,
struct damon_target *t);
void damon_add_region(struct damon_region *r, struct damon_target *t);
void damon_destroy_region(struct damon_region *r, struct damon_target *t);
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(unsigned long id);
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_targets(struct damon_ctx *ctx,
unsigned long *ids, ssize_t nr_ids);
int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
unsigned long aggr_int, unsigned long primitive_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);
int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
#endif /* CONFIG_DAMON */
/* Monitoring primitives for virtual memory address spaces */
void damon_va_init(struct damon_ctx *ctx);
void damon_va_update(struct damon_ctx *ctx);
void damon_va_prepare_access_checks(struct damon_ctx *ctx);
unsigned int damon_va_check_accesses(struct damon_ctx *ctx);
bool damon_va_target_valid(void *t);
void damon_va_cleanup(struct damon_ctx *ctx);
int damon_va_apply_scheme(struct damon_ctx *context, struct damon_target *t,
struct damon_region *r, struct damos *scheme);
int damon_va_scheme_score(struct damon_ctx *context, struct damon_target *t,
struct damon_region *r, struct damos *scheme);
void damon_va_set_primitives(struct damon_ctx *ctx);
/* Monitoring primitives for the physical memory address space */
void damon_pa_prepare_access_checks(struct damon_ctx *ctx);
unsigned int damon_pa_check_accesses(struct damon_ctx *ctx);
bool damon_pa_target_valid(void *t);
int damon_pa_apply_scheme(struct damon_ctx *context, struct damon_target *t,
struct damon_region *r, struct damos *scheme);
int damon_pa_scheme_score(struct damon_ctx *context, struct damon_target *t,
struct damon_region *r, struct damos *scheme);
void damon_pa_set_primitives(struct damon_ctx *ctx);
#endif /* _DAMON_H */