From: SeongJae Park <sjpark@xxxxxxxxx>
If there are too large memory regions fulfilling the target data access
pattern of a DAMON-based operation scheme, applying the action of the
scheme could consume too much CPU. To avoid that, this commit
implements a limit for the action application speed. Using the feature,
the client can set up to how much amount of memory regions the action
could applied within specific time duration.
Signed-off-by: SeongJae Park <sjpark@xxxxxxxxx>
---
include/linux/damon.h | 34 +++++++++++++++++++++++++++----
mm/damon/core.c | 47 +++++++++++++++++++++++++++++++++++++------
mm/damon/dbgfs.c | 4 +++-
3 files changed, 74 insertions(+), 11 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index 684a3603ddac..35068b0ece6f 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -87,6 +87,25 @@ enum damos_action {
DAMOS_STAT, /* Do nothing but only record the stat */
};
+/**
+ * struct damos_speed_limit - Controls the aggressiveness of the given scheme.
+ * @sz: Scheme action amount limit in bytes.
+ * @ms: Scheme action amount charge duration.
+ *
+ * To avoid consuming too much CPU time for applying the &struct damos->action
+ * to large memory, DAMON applies it to only up to &sz bytes within &ms.
+ *
+ * If &sz is 0, the limit is disabled.
+ */
+struct damos_speed_limit {
+ unsigned long sz;
+ unsigned long ms;
+
+/* private: for limit accounting */
+ unsigned long charged_sz;
+ unsigned long charged_from;
+};
+
/**
* struct damos - Represents a Data Access Monitoring-based Operation Scheme.
* @min_sz_region: Minimum size of target regions.
@@ -96,13 +115,19 @@ enum damos_action {
* @min_age_region: Minimum age of target regions.
* @max_age_region: Maximum age of target regions.
* @action: &damo_action to be applied to the target regions.
+ * @limit: Control the aggressiveness 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.
*
- * For each aggregation interval, DAMON applies @action to monitoring target
- * regions fit in the condition and updates the statistics. Note that both
- * the minimums and the maximums are inclusive.
+ * For each aggregation interval, DAMON finds regions which fit in the
+ * condition (&min_sz_region, &max_sz_region, &min_nr_accesses,
+ * &max_nr_accesses, &min_age_region, &max_age_region) and applies &action to
+ * those. To avoid consuming too much CPU for the &action, &limit is used.
+ *
+ * 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.
*/
struct damos {
unsigned long min_sz_region;
@@ -112,6 +137,7 @@ struct damos {
unsigned int min_age_region;
unsigned int max_age_region;
enum damos_action action;
+ struct damos_speed_limit limit;
unsigned long stat_count;
unsigned long stat_sz;
struct list_head list;
@@ -335,7 +361,7 @@ 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);
+ enum damos_action action, struct damos_speed_limit *limit);
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 a33b3a3b9e57..df784c72ea80 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -85,7 +85,7 @@ 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)
+ enum damos_action action, struct damos_speed_limit *limit)
{
struct damos *scheme;
@@ -103,6 +103,11 @@ struct damos *damon_new_scheme(
scheme->stat_sz = 0;
INIT_LIST_HEAD(&scheme->list);
+ scheme->limit.sz = limit->sz;
+ scheme->limit.ms = limit->ms;
+ scheme->limit.charged_sz = 0;
+ scheme->limit.charged_from = 0;
+
return scheme;
}
@@ -536,6 +541,9 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
}
}
+static void damon_split_region_at(struct damon_ctx *ctx,
+ struct damon_region *r, unsigned long sz_r);
+
static void damon_do_apply_schemes(struct damon_ctx *c,
struct damon_target *t,
struct damon_region *r)
@@ -544,7 +552,14 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
unsigned long sz;
damon_for_each_scheme(s, c) {
+ struct damos_speed_limit *limit = &s->limit;
+
+ /* Check the limit */
+ if (limit->sz && limit->charged_sz >= limit->sz)
+ continue;
+
sz = r->ar.end - r->ar.start;
+ /* Check the target regions condition */
if (sz < s->min_sz_region || s->max_sz_region < sz)
continue;
if (r->nr_accesses < s->min_nr_accesses ||
@@ -552,22 +567,42 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
continue;
if (r->age < s->min_age_region || s->max_age_region < r->age)
continue;
- s->stat_count++;
- s->stat_sz += sz;
- if (c->primitive.apply_scheme)
+
+ /* Apply the scheme */
+ if (c->primitive.apply_scheme) {
+ if (limit->sz && limit->charged_sz + sz > limit->sz) {
+ sz = limit->sz - limit->charged_sz;
+ damon_split_region_at(c, r, sz);
+ }
c->primitive.apply_scheme(c, t, r, s);
+ limit->charged_sz += sz;
+ }
if (s->action != DAMOS_STAT)
r->age = 0;
+
+ /* Update stat */
+ s->stat_count++;
+ s->stat_sz += sz;
}
}
static void kdamond_apply_schemes(struct damon_ctx *c)
{
struct damon_target *t;
- struct damon_region *r;
+ struct damon_region *r, *next_r;
+ struct damos *s;
+
+ damon_for_each_scheme(s, c) {
+ /* Reset charge window if the duration passed */
+ if (time_after_eq(jiffies, s->limit.charged_from +
+ msecs_to_jiffies(s->limit.ms))) {
+ s->limit.charged_from = jiffies;
+ s->limit.charged_sz = 0;
+ }
+ }
damon_for_each_target(t, c) {
- damon_for_each_region(r, t)
+ damon_for_each_region_safe(r, next_r, t)
damon_do_apply_schemes(c, t, r);
}
}
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 5b254eccdb43..4b45b69db697 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -310,6 +310,8 @@ 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_speed_limit limit = {};
+
ret = sscanf(&str[pos], "%lu %lu %u %u %u %u %u%n",
&min_sz, &max_sz, &min_nr_a, &max_nr_a,
&min_age, &max_age, &action, &parsed);
@@ -322,7 +324,7 @@ 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);
+ min_age, max_age, action, &limit);
if (!scheme)
goto fail;
--
2.17.1
