168 lines
6.6 KiB
C
168 lines
6.6 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* DAMON api
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*
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* Author: SeongJae Park <sjpark@amazon.de>
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*/
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#ifndef _DAMON_H_
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#define _DAMON_H_
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#include <linux/mutex.h>
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#include <linux/time64.h>
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#include <linux/types.h>
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struct damon_ctx;
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/**
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* struct damon_primitive Monitoring primitives for given use cases.
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*
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* @init: Initialize primitive-internal data structures.
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* @update: Update primitive-internal data structures.
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* @prepare_access_checks: Prepare next access check of target regions.
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* @check_accesses: Check the accesses to target regions.
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* @reset_aggregated: Reset aggregated accesses monitoring results.
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* @target_valid: Determine if the target is valid.
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* @cleanup: Clean up the context.
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*
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* DAMON can be extended for various address spaces and usages. For this,
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* users should register the low level primitives for their target address
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* space and usecase via the &damon_ctx.primitive. Then, the monitoring thread
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* (&damon_ctx.kdamond) calls @init and @prepare_access_checks before starting
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* the monitoring, @update after each &damon_ctx.primitive_update_interval, and
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* @check_accesses, @target_valid and @prepare_access_checks after each
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* &damon_ctx.sample_interval. Finally, @reset_aggregated is called after each
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* &damon_ctx.aggr_interval.
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*
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* @init should initialize primitive-internal data structures. For example,
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* this could be used to construct proper monitoring target regions and link
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* those to @damon_ctx.target.
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* @update should update the primitive-internal data structures. For example,
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* this could be used to update monitoring target regions for current status.
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* @prepare_access_checks should manipulate the monitoring regions to be
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* prepared for the next access check.
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* @check_accesses should check the accesses to each region that made after the
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* last preparation and update the number of observed accesses of each region.
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* @reset_aggregated should reset the access monitoring results that aggregated
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* by @check_accesses.
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* @target_valid should check whether the target is still valid for the
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* monitoring.
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* @cleanup is called from @kdamond just before its termination.
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*/
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struct damon_primitive {
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void (*init)(struct damon_ctx *context);
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void (*update)(struct damon_ctx *context);
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void (*prepare_access_checks)(struct damon_ctx *context);
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void (*check_accesses)(struct damon_ctx *context);
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void (*reset_aggregated)(struct damon_ctx *context);
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bool (*target_valid)(void *target);
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void (*cleanup)(struct damon_ctx *context);
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};
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/*
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* struct damon_callback Monitoring events notification callbacks.
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*
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* @before_start: Called before starting the monitoring.
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* @after_sampling: Called after each sampling.
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* @after_aggregation: Called after each aggregation.
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* @before_terminate: Called before terminating the monitoring.
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* @private: User private data.
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*
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* The monitoring thread (&damon_ctx.kdamond) calls @before_start and
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* @before_terminate just before starting and finishing the monitoring,
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* respectively. Therefore, those are good places for installing and cleaning
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* @private.
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*
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* The monitoring thread calls @after_sampling and @after_aggregation for each
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* of the sampling intervals and aggregation intervals, respectively.
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* Therefore, users can safely access the monitoring results without additional
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* protection. For the reason, users are recommended to use these callback for
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* the accesses to the results.
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*
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* If any callback returns non-zero, monitoring stops.
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*/
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struct damon_callback {
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void *private;
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int (*before_start)(struct damon_ctx *context);
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int (*after_sampling)(struct damon_ctx *context);
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int (*after_aggregation)(struct damon_ctx *context);
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int (*before_terminate)(struct damon_ctx *context);
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};
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/**
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* struct damon_ctx - Represents a context for each monitoring. This is the
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* main interface that allows users to set the attributes and get the results
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* of the monitoring.
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*
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* @sample_interval: The time between access samplings.
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* @aggr_interval: The time between monitor results aggregations.
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* @primitive_update_interval: The time between monitoring primitive updates.
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*
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* For each @sample_interval, DAMON checks whether each region is accessed or
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* not. It aggregates and keeps the access information (number of accesses to
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* each region) for @aggr_interval time. DAMON also checks whether the target
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* memory regions need update (e.g., by ``mmap()`` calls from the application,
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* in case of virtual memory monitoring) and applies the changes for each
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* @primitive_update_interval. All time intervals are in micro-seconds.
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* Please refer to &struct damon_primitive and &struct damon_callback for more
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* detail.
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*
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* @kdamond: Kernel thread who does the monitoring.
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* @kdamond_stop: Notifies whether kdamond should stop.
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* @kdamond_lock: Mutex for the synchronizations with @kdamond.
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*
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* For each monitoring context, one kernel thread for the monitoring is
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* created. The pointer to the thread is stored in @kdamond.
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*
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* Once started, the monitoring thread runs until explicitly required to be
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* terminated or every monitoring target is invalid. The validity of the
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* targets is checked via the &damon_primitive.target_valid of @primitive. The
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* termination can also be explicitly requested by writing non-zero to
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* @kdamond_stop. The thread sets @kdamond to NULL when it terminates.
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* Therefore, users can know whether the monitoring is ongoing or terminated by
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* reading @kdamond. Reads and writes to @kdamond and @kdamond_stop from
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* outside of the monitoring thread must be protected by @kdamond_lock.
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*
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* Note that the monitoring thread protects only @kdamond and @kdamond_stop via
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* @kdamond_lock. Accesses to other fields must be protected by themselves.
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*
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* @primitive: Set of monitoring primitives for given use cases.
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* @callback: Set of callbacks for monitoring events notifications.
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*
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* @target: Pointer to the user-defined monitoring target.
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*/
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struct damon_ctx {
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unsigned long sample_interval;
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unsigned long aggr_interval;
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unsigned long primitive_update_interval;
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/* private: internal use only */
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struct timespec64 last_aggregation;
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struct timespec64 last_primitive_update;
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/* public: */
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struct task_struct *kdamond;
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bool kdamond_stop;
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struct mutex kdamond_lock;
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struct damon_primitive primitive;
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struct damon_callback callback;
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void *target;
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};
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#ifdef CONFIG_DAMON
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struct damon_ctx *damon_new_ctx(void);
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void damon_destroy_ctx(struct damon_ctx *ctx);
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int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
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unsigned long aggr_int, unsigned long primitive_upd_int);
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int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
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int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
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#endif /* CONFIG_DAMON */
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#endif /* _DAMON_H */
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