[linux-block.git] / mm / damon / reclaim.c

// SPDX-License-Identifier: GPL-2.0
/*
 * DAMON-based page reclamation
 *
 * Author: SeongJae Park <sj@kernel.org>
 */

#define pr_fmt(fmt) "damon-reclaim: " fmt

#include <linux/damon.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/workqueue.h>

#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "damon_reclaim."

/*
 * Enable or disable DAMON_RECLAIM.
 *
 * You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``.
 * Setting it as ``N`` disables DAMON_RECLAIM.  Note that DAMON_RECLAIM could
 * do no real monitoring and reclamation due to the watermarks-based activation
 * condition.  Refer to below descriptions for the watermarks parameter for
 * this.
 */
static bool enabled __read_mostly;
module_param(enabled, bool, 0600);

/*
 * Time threshold for cold memory regions identification in microseconds.
 *
 * If a memory region is not accessed for this or longer time, DAMON_RECLAIM
 * identifies the region as cold, and reclaims.  120 seconds by default.
 */
static unsigned long min_age __read_mostly = 120000000;
module_param(min_age, ulong, 0600);

/*
 * Limit of time for trying the reclamation in milliseconds.
 *
 * DAMON_RECLAIM tries to use only up to this time within a time window
 * (quota_reset_interval_ms) for trying reclamation of cold pages.  This can be
 * used for limiting CPU consumption of DAMON_RECLAIM.  If the value is zero,
 * the limit is disabled.
 *
 * 10 ms by default.
 */
static unsigned long quota_ms __read_mostly = 10;
module_param(quota_ms, ulong, 0600);

/*
 * Limit of size of memory for the reclamation in bytes.
 *
 * DAMON_RECLAIM charges amount of memory which it tried to reclaim within a
 * time window (quota_reset_interval_ms) and makes no more than this limit is
 * tried.  This can be used for limiting consumption of CPU and IO.  If this
 * value is zero, the limit is disabled.
 *
 * 128 MiB by default.
 */
static unsigned long quota_sz __read_mostly = 128 * 1024 * 1024;
module_param(quota_sz, ulong, 0600);

/*
 * The time/size quota charge reset interval in milliseconds.
 *
 * The charge reset interval for the quota of time (quota_ms) and size
 * (quota_sz).  That is, DAMON_RECLAIM does not try reclamation for more than
 * quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms
 * milliseconds.
 *
 * 1 second by default.
 */
static unsigned long quota_reset_interval_ms __read_mostly = 1000;
module_param(quota_reset_interval_ms, ulong, 0600);

/*
 * The watermarks check time interval in microseconds.
 *
 * Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is
 * enabled but inactive due to its watermarks rule.  5 seconds by default.
 */
static unsigned long wmarks_interval __read_mostly = 5000000;
module_param(wmarks_interval, ulong, 0600);

/*
 * Free memory rate (per thousand) for the high watermark.
 *
 * If free memory of the system in bytes per thousand bytes is higher than
 * this, DAMON_RECLAIM becomes inactive, so it does nothing but periodically
 * checks the watermarks.  500 (50%) by default.
 */
static unsigned long wmarks_high __read_mostly = 500;
module_param(wmarks_high, ulong, 0600);

/*
 * Free memory rate (per thousand) for the middle watermark.
 *
 * If free memory of the system in bytes per thousand bytes is between this and
 * the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring
 * and the reclaiming.  400 (40%) by default.
 */
static unsigned long wmarks_mid __read_mostly = 400;
module_param(wmarks_mid, ulong, 0600);

/*
 * Free memory rate (per thousand) for the low watermark.
 *
 * If free memory of the system in bytes per thousand bytes is lower than this,
 * DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks
 * the watermarks.  In the case, the system falls back to the LRU-based page
 * granularity reclamation logic.  200 (20%) by default.
 */
static unsigned long wmarks_low __read_mostly = 200;
module_param(wmarks_low, ulong, 0600);

/*
 * Sampling interval for the monitoring in microseconds.
 *
 * The sampling interval of DAMON for the cold memory monitoring.  Please refer
 * to the DAMON documentation for more detail.  5 ms by default.
 */
static unsigned long sample_interval __read_mostly = 5000;
module_param(sample_interval, ulong, 0600);

/*
 * Aggregation interval for the monitoring in microseconds.
 *
 * The aggregation interval of DAMON for the cold memory monitoring.  Please
 * refer to the DAMON documentation for more detail.  100 ms by default.
 */
static unsigned long aggr_interval __read_mostly = 100000;
module_param(aggr_interval, ulong, 0600);

/*
 * Minimum number of monitoring regions.
 *
 * The minimal number of monitoring regions of DAMON for the cold memory
 * monitoring.  This can be used to set lower-bound of the monitoring quality.
 * But, setting this too high could result in increased monitoring overhead.
 * Please refer to the DAMON documentation for more detail.  10 by default.
 */
static unsigned long min_nr_regions __read_mostly = 10;
module_param(min_nr_regions, ulong, 0600);

/*
 * Maximum number of monitoring regions.
 *
 * The maximum number of monitoring regions of DAMON for the cold memory
 * monitoring.  This can be used to set upper-bound of the monitoring overhead.
 * However, setting this too low could result in bad monitoring quality.
 * Please refer to the DAMON documentation for more detail.  1000 by default.
 */
static unsigned long max_nr_regions __read_mostly = 1000;
module_param(max_nr_regions, ulong, 0600);

/*
 * Start of the target memory region in physical address.
 *
 * The start physical address of memory region that DAMON_RECLAIM will do work
 * against.  By default, biggest System RAM is used as the region.
 */
static unsigned long monitor_region_start __read_mostly;
module_param(monitor_region_start, ulong, 0600);

/*
 * End of the target memory region in physical address.
 *
 * The end physical address of memory region that DAMON_RECLAIM will do work
 * against.  By default, biggest System RAM is used as the region.
 */
static unsigned long monitor_region_end __read_mostly;
module_param(monitor_region_end, ulong, 0600);

/*
 * PID of the DAMON thread
 *
 * If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.
 * Else, -1.
 */
static int kdamond_pid __read_mostly = -1;
module_param(kdamond_pid, int, 0400);

/*
 * Number of memory regions that tried to be reclaimed.
 */
static unsigned long nr_reclaim_tried_regions __read_mostly;
module_param(nr_reclaim_tried_regions, ulong, 0400);

/*
 * Total bytes of memory regions that tried to be reclaimed.
 */
static unsigned long bytes_reclaim_tried_regions __read_mostly;
module_param(bytes_reclaim_tried_regions, ulong, 0400);

/*
 * Number of memory regions that successfully be reclaimed.
 */
static unsigned long nr_reclaimed_regions __read_mostly;
module_param(nr_reclaimed_regions, ulong, 0400);

/*
 * Total bytes of memory regions that successfully be reclaimed.
 */
static unsigned long bytes_reclaimed_regions __read_mostly;
module_param(bytes_reclaimed_regions, ulong, 0400);

/*
 * Number of times that the time/space quota limits have exceeded
 */
static unsigned long nr_quota_exceeds __read_mostly;
module_param(nr_quota_exceeds, ulong, 0400);

static struct damon_ctx *ctx;
static struct damon_target *target;

struct damon_reclaim_ram_walk_arg {
	unsigned long start;
	unsigned long end;
};

static int walk_system_ram(struct resource *res, void *arg)
{
	struct damon_reclaim_ram_walk_arg *a = arg;

	if (a->end - a->start < res->end - res->start) {
		a->start = res->start;
		a->end = res->end;
	}
	return 0;
}

/*
 * Find biggest 'System RAM' resource and store its start and end address in
 * @start and @end, respectively.  If no System RAM is found, returns false.
 */
static bool get_monitoring_region(unsigned long *start, unsigned long *end)
{
	struct damon_reclaim_ram_walk_arg arg = {};

	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
	if (arg.end <= arg.start)
		return false;

	*start = arg.start;
	*end = arg.end;
	return true;
}

static struct damos *damon_reclaim_new_scheme(void)
{
	struct damos_watermarks wmarks = {
		.metric = DAMOS_WMARK_FREE_MEM_RATE,
		.interval = wmarks_interval,
		.high = wmarks_high,
		.mid = wmarks_mid,
		.low = wmarks_low,
	};
	struct damos_quota quota = {
		/*
		 * Do not try reclamation for more than quota_ms milliseconds
		 * or quota_sz bytes within quota_reset_interval_ms.
		 */
		.ms = quota_ms,
		.sz = quota_sz,
		.reset_interval = quota_reset_interval_ms,
		/* Within the quota, page out older regions first. */
		.weight_sz = 0,
		.weight_nr_accesses = 0,
		.weight_age = 1
	};
	struct damos *scheme = damon_new_scheme(
			/* Find regions having PAGE_SIZE or larger size */
			PAGE_SIZE, ULONG_MAX,
			/* and not accessed at all */
			0, 0,
			/* for min_age or more micro-seconds, and */
			min_age / aggr_interval, UINT_MAX,
			/* page out those, as soon as found */
			DAMOS_PAGEOUT,
			/* under the quota. */
			&quota,
			/* (De)activate this according to the watermarks. */
			&wmarks);

	return scheme;
}

static int damon_reclaim_turn(bool on)
{
	struct damon_region *region;
	struct damos *scheme;
	int err;

	if (!on) {
		err = damon_stop(&ctx, 1);
		if (!err)
			kdamond_pid = -1;
		return err;
	}

	err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
			min_nr_regions, max_nr_regions);
	if (err)
		return err;

	if (monitor_region_start > monitor_region_end)
		return -EINVAL;
	if (!monitor_region_start && !monitor_region_end &&
			!get_monitoring_region(&monitor_region_start,
				&monitor_region_end))
		return -EINVAL;
	/* DAMON will free this on its own when finish monitoring */
	region = damon_new_region(monitor_region_start, monitor_region_end);
	if (!region)
		return -ENOMEM;
	damon_add_region(region, target);

	/* Will be freed by 'damon_set_schemes()' below */
	scheme = damon_reclaim_new_scheme();
	if (!scheme) {
		err = -ENOMEM;
		goto free_region_out;
	}
	err = damon_set_schemes(ctx, &scheme, 1);
	if (err)
		goto free_scheme_out;

	err = damon_start(&ctx, 1);
	if (!err) {
		kdamond_pid = ctx->kdamond->pid;
		return 0;
	}

free_scheme_out:
	damon_destroy_scheme(scheme);
free_region_out:
	damon_destroy_region(region, target);
	return err;
}

#define ENABLE_CHECK_INTERVAL_MS	1000
static struct delayed_work damon_reclaim_timer;
static void damon_reclaim_timer_fn(struct work_struct *work)
{
	static bool last_enabled;
	bool now_enabled;

	now_enabled = enabled;
	if (last_enabled != now_enabled) {
		if (!damon_reclaim_turn(now_enabled))
			last_enabled = now_enabled;
		else
			enabled = last_enabled;
	}

	schedule_delayed_work(&damon_reclaim_timer,
			msecs_to_jiffies(ENABLE_CHECK_INTERVAL_MS));
}
static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);

static int damon_reclaim_after_aggregation(struct damon_ctx *c)
{
	struct damos *s;

	/* update the stats parameter */
	damon_for_each_scheme(s, c) {
		nr_reclaim_tried_regions = s->stat.nr_tried;
		bytes_reclaim_tried_regions = s->stat.sz_tried;
		nr_reclaimed_regions = s->stat.nr_applied;
		bytes_reclaimed_regions = s->stat.sz_applied;
		nr_quota_exceeds = s->stat.qt_exceeds;
	}
	return 0;
}

static int __init damon_reclaim_init(void)
{
	ctx = damon_new_ctx();
	if (!ctx)
		return -ENOMEM;

	damon_pa_set_primitives(ctx);
	ctx->callback.after_aggregation = damon_reclaim_after_aggregation;

	/* 4242 means nothing but fun */
	target = damon_new_target(4242);
	if (!target) {
		damon_destroy_ctx(ctx);
		return -ENOMEM;
	}
	damon_add_target(ctx, target);

	schedule_delayed_work(&damon_reclaim_timer, 0);
	return 0;
}

module_init(damon_reclaim_init);
Commit	Line	Data
43b0536c SP	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* DAMON-based page reclamation
	4	*
	5	* Author: SeongJae Park <sj@kernel.org>
	6	*/
	7
	8	#define pr_fmt(fmt) "damon-reclaim: " fmt
	9
	10	#include <linux/damon.h>
	11	#include <linux/ioport.h>
	12	#include <linux/module.h>
	13	#include <linux/sched.h>
	14	#include <linux/workqueue.h>
	15
	16	#ifdef MODULE_PARAM_PREFIX
	17	#undef MODULE_PARAM_PREFIX
	18	#endif
	19	#define MODULE_PARAM_PREFIX "damon_reclaim."
	20
	21	/*
	22	* Enable or disable DAMON_RECLAIM.
	23	*
	24	* You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``.
	25	* Setting it as ``N`` disables DAMON_RECLAIM. Note that DAMON_RECLAIM could
	26	* do no real monitoring and reclamation due to the watermarks-based activation
	27	* condition. Refer to below descriptions for the watermarks parameter for
	28	* this.
	29	*/
	30	static bool enabled __read_mostly;
	31	module_param(enabled, bool, 0600);
	32
	33	/*
	34	* Time threshold for cold memory regions identification in microseconds.
	35	*
	36	* If a memory region is not accessed for this or longer time, DAMON_RECLAIM
	37	* identifies the region as cold, and reclaims. 120 seconds by default.
	38	*/
	39	static unsigned long min_age __read_mostly = 120000000;
	40	module_param(min_age, ulong, 0600);
	41
	42	/*
	43	* Limit of time for trying the reclamation in milliseconds.
	44	*
	45	* DAMON_RECLAIM tries to use only up to this time within a time window
	46	* (quota_reset_interval_ms) for trying reclamation of cold pages. This can be
	47	* used for limiting CPU consumption of DAMON_RECLAIM. If the value is zero,
	48	* the limit is disabled.
	49	*
	50	* 10 ms by default.
	51	*/
	52	static unsigned long quota_ms __read_mostly = 10;
	53	module_param(quota_ms, ulong, 0600);
	54
	55	/*
	56	* Limit of size of memory for the reclamation in bytes.
	57	*
	58	* DAMON_RECLAIM charges amount of memory which it tried to reclaim within a
	59	* time window (quota_reset_interval_ms) and makes no more than this limit is
	60	* tried. This can be used for limiting consumption of CPU and IO. If this
	61	* value is zero, the limit is disabled.
	62	*
	63	* 128 MiB by default.
	64	*/
65	static unsigned long quota_sz __read_mostly = 128 * 1024 * 1024;
66	module_param(quota_sz, ulong, 0600);
67
68	/*
69	* The time/size quota charge reset interval in milliseconds.
70	*
71	* The charge reset interval for the quota of time (quota_ms) and size
72	* (quota_sz). That is, DAMON_RECLAIM does not try reclamation for more than
73	* quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms
74	* milliseconds.
75	*
76	* 1 second by default.
77	*/
78	static unsigned long quota_reset_interval_ms __read_mostly = 1000;
79	module_param(quota_reset_interval_ms, ulong, 0600);
80
81	/*
82	* The watermarks check time interval in microseconds.
83	*
84	* Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is
85	* enabled but inactive due to its watermarks rule. 5 seconds by default.
86	*/
87	static unsigned long wmarks_interval __read_mostly = 5000000;
88	module_param(wmarks_interval, ulong, 0600);
89
90	/*
91	* Free memory rate (per thousand) for the high watermark.
92	*
93	* If free memory of the system in bytes per thousand bytes is higher than
94	* this, DAMON_RECLAIM becomes inactive, so it does nothing but periodically
95	* checks the watermarks. 500 (50%) by default.
96	*/
97	static unsigned long wmarks_high __read_mostly = 500;
98	module_param(wmarks_high, ulong, 0600);
99
100	/*
101	* Free memory rate (per thousand) for the middle watermark.
102	*
103	* If free memory of the system in bytes per thousand bytes is between this and
104	* the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring
105	* and the reclaiming. 400 (40%) by default.
106	*/
107	static unsigned long wmarks_mid __read_mostly = 400;
108	module_param(wmarks_mid, ulong, 0600);
109
110	/*
111	* Free memory rate (per thousand) for the low watermark.
112	*
113	* If free memory of the system in bytes per thousand bytes is lower than this,
114	* DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks
115	* the watermarks. In the case, the system falls back to the LRU-based page
116	* granularity reclamation logic. 200 (20%) by default.
117	*/
118	static unsigned long wmarks_low __read_mostly = 200;
119	module_param(wmarks_low, ulong, 0600);
120
121	/*
122	* Sampling interval for the monitoring in microseconds.
123	*
124	* The sampling interval of DAMON for the cold memory monitoring. Please refer
125	* to the DAMON documentation for more detail. 5 ms by default.
126	*/
127	static unsigned long sample_interval __read_mostly = 5000;
128	module_param(sample_interval, ulong, 0600);
129
130	/*
131	* Aggregation interval for the monitoring in microseconds.
132	*
133	* The aggregation interval of DAMON for the cold memory monitoring. Please
134	* refer to the DAMON documentation for more detail. 100 ms by default.
135	*/
136	static unsigned long aggr_interval __read_mostly = 100000;
137	module_param(aggr_interval, ulong, 0600);
138
139	/*
140	* Minimum number of monitoring regions.
141	*
142	* The minimal number of monitoring regions of DAMON for the cold memory
143	* monitoring. This can be used to set lower-bound of the monitoring quality.
144	* But, setting this too high could result in increased monitoring overhead.
145	* Please refer to the DAMON documentation for more detail. 10 by default.
146	*/
147	static unsigned long min_nr_regions __read_mostly = 10;
148	module_param(min_nr_regions, ulong, 0600);
149
150	/*
151	* Maximum number of monitoring regions.
152	*
153	* The maximum number of monitoring regions of DAMON for the cold memory
154	* monitoring. This can be used to set upper-bound of the monitoring overhead.
155	* However, setting this too low could result in bad monitoring quality.
156	* Please refer to the DAMON documentation for more detail. 1000 by default.
157	*/
158	static unsigned long max_nr_regions __read_mostly = 1000;
159	module_param(max_nr_regions, ulong, 0600);
160
161	/*
162	* Start of the target memory region in physical address.
163	*
164	* The start physical address of memory region that DAMON_RECLAIM will do work
165	* against. By default, biggest System RAM is used as the region.
166	*/
167	static unsigned long monitor_region_start __read_mostly;
168	module_param(monitor_region_start, ulong, 0600);
169
170	/*
171	* End of the target memory region in physical address.
172	*
173	* The end physical address of memory region that DAMON_RECLAIM will do work
174	* against. By default, biggest System RAM is used as the region.
175	*/
176	static unsigned long monitor_region_end __read_mostly;
177	module_param(monitor_region_end, ulong, 0600);
178
179	/*
180	* PID of the DAMON thread
181	*
182	* If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.
183	* Else, -1.
184	*/
185	static int kdamond_pid __read_mostly = -1;
186	module_param(kdamond_pid, int, 0400);
187
60e52e7c SP	188	/*
	189	* Number of memory regions that tried to be reclaimed.
	190	*/
	191	static unsigned long nr_reclaim_tried_regions __read_mostly;
	192	module_param(nr_reclaim_tried_regions, ulong, 0400);
	193
	194	/*
	195	* Total bytes of memory regions that tried to be reclaimed.
	196	*/
	197	static unsigned long bytes_reclaim_tried_regions __read_mostly;
	198	module_param(bytes_reclaim_tried_regions, ulong, 0400);
	199
	200	/*
	201	* Number of memory regions that successfully be reclaimed.
	202	*/
	203	static unsigned long nr_reclaimed_regions __read_mostly;
	204	module_param(nr_reclaimed_regions, ulong, 0400);
	205
	206	/*
	207	* Total bytes of memory regions that successfully be reclaimed.
	208	*/
	209	static unsigned long bytes_reclaimed_regions __read_mostly;
	210	module_param(bytes_reclaimed_regions, ulong, 0400);
	211
	212	/*
	213	* Number of times that the time/space quota limits have exceeded
	214	*/
	215	static unsigned long nr_quota_exceeds __read_mostly;
	216	module_param(nr_quota_exceeds, ulong, 0400);
	217
43b0536c SP	218	static struct damon_ctx *ctx;
	219	static struct damon_target *target;
	220
	221	struct damon_reclaim_ram_walk_arg {
	222	unsigned long start;
	223	unsigned long end;
	224	};
	225
	226	static int walk_system_ram(struct resource res, void arg)
	227	{
	228	struct damon_reclaim_ram_walk_arg *a = arg;
	229
	230	if (a->end - a->start < res->end - res->start) {
	231	a->start = res->start;
	232	a->end = res->end;
	233	}
	234	return 0;
	235	}
	236
	237	/*
	238	* Find biggest 'System RAM' resource and store its start and end address in
	239	* @start and @end, respectively. If no System RAM is found, returns false.
	240	*/
	241	static bool get_monitoring_region(unsigned long start, unsigned long end)
	242	{
	243	struct damon_reclaim_ram_walk_arg arg = {};
	244
	245	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
	246	if (arg.end <= arg.start)
	247	return false;
	248
	249	*start = arg.start;
	250	*end = arg.end;
	251	return true;
	252	}
	253
	254	static struct damos *damon_reclaim_new_scheme(void)
	255	{
	256	struct damos_watermarks wmarks = {
	257	.metric = DAMOS_WMARK_FREE_MEM_RATE,
	258	.interval = wmarks_interval,
	259	.high = wmarks_high,
	260	.mid = wmarks_mid,
	261	.low = wmarks_low,
	262	};
	263	struct damos_quota quota = {
	264	/*
	265	* Do not try reclamation for more than quota_ms milliseconds
	266	* or quota_sz bytes within quota_reset_interval_ms.
	267	*/
	268	.ms = quota_ms,
	269	.sz = quota_sz,
	270	.reset_interval = quota_reset_interval_ms,
	271	/* Within the quota, page out older regions first. */
	272	.weight_sz = 0,
	273	.weight_nr_accesses = 0,
	274	.weight_age = 1
	275	};
	276	struct damos *scheme = damon_new_scheme(
	277	/* Find regions having PAGE_SIZE or larger size */
	278	PAGE_SIZE, ULONG_MAX,
	279	/* and not accessed at all */
	280	0, 0,
	281	/* for min_age or more micro-seconds, and */
282	min_age / aggr_interval, UINT_MAX,
283	/* page out those, as soon as found */
284	DAMOS_PAGEOUT,
285	/* under the quota. */
286	&quota,
287	/* (De)activate this according to the watermarks. */
288	&wmarks);
289
290	return scheme;
291	}
292
293	static int damon_reclaim_turn(bool on)
294	{
295	struct damon_region *region;
296	struct damos *scheme;
297	int err;
298
299	if (!on) {
300	err = damon_stop(&ctx, 1);
301	if (!err)
302	kdamond_pid = -1;
303	return err;
304	}
305
306	err = damon_set_attrs(ctx, sample_interval, aggr_interval, 0,
307	min_nr_regions, max_nr_regions);
308	if (err)
309	return err;
310
311	if (monitor_region_start > monitor_region_end)
312	return -EINVAL;
313	if (!monitor_region_start && !monitor_region_end &&
314	!get_monitoring_region(&monitor_region_start,
315	&monitor_region_end))
316	return -EINVAL;
317	/* DAMON will free this on its own when finish monitoring */
318	region = damon_new_region(monitor_region_start, monitor_region_end);
319	if (!region)
320	return -ENOMEM;
321	damon_add_region(region, target);
322
323	/* Will be freed by 'damon_set_schemes()' below */
324	scheme = damon_reclaim_new_scheme();
325	if (!scheme) {
326	err = -ENOMEM;
327	goto free_region_out;
328	}
329	err = damon_set_schemes(ctx, &scheme, 1);
330	if (err)
331	goto free_scheme_out;
332
333	err = damon_start(&ctx, 1);
334	if (!err) {
335	kdamond_pid = ctx->kdamond->pid;
336	return 0;
337	}
338
339	free_scheme_out:
340	damon_destroy_scheme(scheme);
341	free_region_out:
342	damon_destroy_region(region, target);
343	return err;
344	}
345
346	#define ENABLE_CHECK_INTERVAL_MS 1000
347	static struct delayed_work damon_reclaim_timer;
348	static void damon_reclaim_timer_fn(struct work_struct *work)
349	{
350	static bool last_enabled;
351	bool now_enabled;
352
353	now_enabled = enabled;
354	if (last_enabled != now_enabled) {
355	if (!damon_reclaim_turn(now_enabled))
356	last_enabled = now_enabled;
357	else
358	enabled = last_enabled;
359	}
360
361	schedule_delayed_work(&damon_reclaim_timer,
362	msecs_to_jiffies(ENABLE_CHECK_INTERVAL_MS));
363	}
364	static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);
365
60e52e7c SP	366	static int damon_reclaim_after_aggregation(struct damon_ctx *c)
	367	{
	368	struct damos *s;
	369
	370	/* update the stats parameter */
	371	damon_for_each_scheme(s, c) {
	372	nr_reclaim_tried_regions = s->stat.nr_tried;
	373	bytes_reclaim_tried_regions = s->stat.sz_tried;
	374	nr_reclaimed_regions = s->stat.nr_applied;
	375	bytes_reclaimed_regions = s->stat.sz_applied;
	376	nr_quota_exceeds = s->stat.qt_exceeds;
	377	}
	378	return 0;
	379	}
	380
43b0536c SP	381	static int __init damon_reclaim_init(void)
	382	{
	383	ctx = damon_new_ctx();
	384	if (!ctx)
	385	return -ENOMEM;
	386
	387	damon_pa_set_primitives(ctx);
60e52e7c	388	ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
43b0536c SP	389
	390	/* 4242 means nothing but fun */
	391	target = damon_new_target(4242);
	392	if (!target) {
	393	damon_destroy_ctx(ctx);
	394	return -ENOMEM;
	395	}
	396	damon_add_target(ctx, target);
	397
	398	schedule_delayed_work(&damon_reclaim_timer, 0);
	399	return 0;
	400	}
	401
	402	module_init(damon_reclaim_init);