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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>
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.target.
* @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.
* @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);
void (*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.
*
* @target: Pointer to the user-defined monitoring target.
*/
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;
void *target;
};
#ifdef CONFIG_DAMON
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 primitive_upd_int);
int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
#endif /* CONFIG_DAMON */
#endif /* _DAMON_H */
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