diff --git a/include/linux/damon.h b/include/linux/damon.h
index 1217566a0ebcff1c616d3ae8a7ccdeb7c8ac3574..c93325efddd7d0053208b4514e34634e049319c3 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -146,6 +146,45 @@ struct damos_quota {
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 {
+ DAMOS_WMARK_NONE,
+ DAMOS_WMARK_FREE_MEM_RATE,
+};
+
+/**
+ * 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.
@@ -156,6 +195,7 @@ struct damos_quota {
* @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.
@@ -166,6 +206,14 @@ struct damos_quota {
* those. To avoid consuming too much CPU time or IO resources for the
* &action, "a 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.
@@ -179,6 +227,7 @@ struct damos {
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;
@@ -384,7 +433,8 @@ 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);
+ 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);
diff --git a/mm/damon/core.c b/mm/damon/core.c
index fad25778e2ecf3ba9c0e6642546461194c08e7c7..6993c60ae31c44146ce78490fe166b6eb7101ad9 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -10,6 +10,7 @@
#include <linux/damon.h>
#include <linux/delay.h>
#include <linux/kthread.h>
+#include <linux/mm.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/string.h>
@@ -90,7 +91,8 @@ 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)
+ enum damos_action action, struct damos_quota *quota,
+ struct damos_watermarks *wmarks)
{
struct damos *scheme;
@@ -122,6 +124,13 @@ struct damos *damon_new_scheme(
scheme->quota.charge_target_from = NULL;
scheme->quota.charge_addr_from = 0;
+ scheme->wmarks.metric = wmarks->metric;
+ scheme->wmarks.interval = wmarks->interval;
+ scheme->wmarks.high = wmarks->high;
+ scheme->wmarks.mid = wmarks->mid;
+ scheme->wmarks.low = wmarks->low;
+ scheme->wmarks.activated = true;
+
return scheme;
}
@@ -582,6 +591,9 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
unsigned long sz = r->ar.end - r->ar.start;
struct timespec64 begin, end;
+ if (!s->wmarks.activated)
+ continue;
+
/* Check the quota */
if (quota->esz && quota->charged_sz >= quota->esz)
continue;
@@ -684,6 +696,9 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
unsigned long cumulated_sz;
unsigned int score, max_score = 0;
+ if (!s->wmarks.activated)
+ continue;
+
if (!quota->ms && !quota->sz)
continue;
@@ -924,6 +939,83 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
return true;
}
+static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
+{
+ struct sysinfo i;
+
+ switch (metric) {
+ case DAMOS_WMARK_FREE_MEM_RATE:
+ si_meminfo(&i);
+ return i.freeram * 1000 / i.totalram;
+ default:
+ break;
+ }
+ return -EINVAL;
+}
+
+/*
+ * Returns zero if the scheme is active. Else, returns time to wait for next
+ * watermark check in micro-seconds.
+ */
+static unsigned long damos_wmark_wait_us(struct damos *scheme)
+{
+ unsigned long metric;
+
+ if (scheme->wmarks.metric == DAMOS_WMARK_NONE)
+ return 0;
+
+ metric = damos_wmark_metric_value(scheme->wmarks.metric);
+ /* higher than high watermark or lower than low watermark */
+ if (metric > scheme->wmarks.high || scheme->wmarks.low > metric) {
+ if (scheme->wmarks.activated)
+ pr_debug("inactivate a scheme (%d) for %s wmark\n",
+ scheme->action,
+ metric > scheme->wmarks.high ?
+ "high" : "low");
+ scheme->wmarks.activated = false;
+ return scheme->wmarks.interval;
+ }
+
+ /* inactive and higher than middle watermark */
+ if ((scheme->wmarks.high >= metric && metric >= scheme->wmarks.mid) &&
+ !scheme->wmarks.activated)
+ return scheme->wmarks.interval;
+
+ if (!scheme->wmarks.activated)
+ pr_debug("activate a scheme (%d)\n", scheme->action);
+ scheme->wmarks.activated = true;
+ return 0;
+}
+
+static void kdamond_usleep(unsigned long usecs)
+{
+ if (usecs > 100 * 1000)
+ schedule_timeout_interruptible(usecs_to_jiffies(usecs));
+ else
+ usleep_range(usecs, usecs + 1);
+}
+
+/* Returns negative error code if it's not activated but should return */
+static int kdamond_wait_activation(struct damon_ctx *ctx)
+{
+ struct damos *s;
+ unsigned long wait_time;
+ unsigned long min_wait_time = 0;
+
+ while (!kdamond_need_stop(ctx)) {
+ damon_for_each_scheme(s, ctx) {
+ wait_time = damos_wmark_wait_us(s);
+ if (!min_wait_time || wait_time < min_wait_time)
+ min_wait_time = wait_time;
+ }
+ if (!min_wait_time)
+ return 0;
+
+ kdamond_usleep(min_wait_time);
+ }
+ return -EBUSY;
+}
+
static void set_kdamond_stop(struct damon_ctx *ctx)
{
mutex_lock(&ctx->kdamond_lock);
@@ -952,6 +1044,9 @@ static int kdamond_fn(void *data)
sz_limit = damon_region_sz_limit(ctx);
while (!kdamond_need_stop(ctx)) {
+ if (kdamond_wait_activation(ctx))
+ continue;
+
if (ctx->primitive.prepare_access_checks)
ctx->primitive.prepare_access_checks(ctx);
if (ctx->callback.after_sampling &&
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 20c4feb8b918c7276d2894aca1d75a529f91b1d4..9f13060d105855e0324bddceca871008d2040208 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -195,6 +195,9 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
*nr_schemes = 0;
while (pos < len && *nr_schemes < max_nr_schemes) {
struct damos_quota quota = {};
+ struct damos_watermarks wmarks = {
+ .metric = DAMOS_WMARK_NONE,
+ };
ret = sscanf(&str[pos],
"%lu %lu %u %u %u %u %u %lu %lu %lu %u %u %u%n",
@@ -212,7 +215,7 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
pos += parsed;
scheme = damon_new_scheme(min_sz, max_sz, min_nr_a, max_nr_a,
- min_age, max_age, action, "a);
+ min_age, max_age, action, "a, &wmarks);
if (!scheme)
goto fail;