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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>
+
+/* Minimal region size. Every damon_region is aligned by this. */
+#define DAMON_MIN_REGION PAGE_SIZE
+
+/**
+ * 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.
+ */
+struct damon_region {
+ struct damon_addr_range ar;
+ unsigned long sampling_addr;
+ unsigned int nr_accesses;
+ struct list_head list;
+};
+
+/**
+ * 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;
+};
+
+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.
+ * @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.
+ * @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);
+ 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);
+ int (*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.
+ */
+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;
+ bool kdamond_stop;
+ 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;
+};
+
+#define damon_next_region(r) \
+ (container_of(r->list.next, struct damon_region, list))
+
+#define damon_prev_region(r) \
+ (container_of(r->list.prev, 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)
+
+#ifdef CONFIG_DAMON
+
+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 damon_target *damon_new_target(unsigned long id);
+void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);
+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_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 */
+
+#ifdef CONFIG_DAMON_VADDR
+
+/* 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);
+void damon_va_set_primitives(struct damon_ctx *ctx);
+
+#endif /* CONFIG_DAMON_VADDR */
+
+#endif /* _DAMON_H */