[RFC v2 07/14] mm/damon/vaddr,paddr: Support pageout prioritization

[SeongJae Park <sj38.park@gmail.com>]

From: SeongJae Park <sjpark@amazon.de>

This commit makes the default monitoring primitives for virtual address
spaces and the physical address sapce to support memory regions
prioritization for 'PAGEOUT' DAMOS action.  It calculates hotness of
each region as weighted sum of 'nr_accesses' and 'age' of the region and
get the priority score as reverse of the hotness, so that cold regions
can be paged out first.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h   |  4 ++++
 mm/damon/paddr.c        | 14 +++++++++++++
 mm/damon/prmtv-common.c | 46 +++++++++++++++++++++++++++++++++++++++++
 mm/damon/prmtv-common.h |  3 +++
 mm/damon/vaddr.c        | 15 ++++++++++++++
 5 files changed, 82 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 8f35bd94fc2b..565f49d8ba44 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -428,6 +428,8 @@ bool damon_va_target_valid(void *t);
 void damon_va_cleanup(struct damon_ctx *ctx);
 int damon_va_apply_scheme(struct damon_ctx *context, struct damon_target *t,
 		struct damon_region *r, struct damos *scheme);
+int damon_va_scheme_score(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme);
 void damon_va_set_primitives(struct damon_ctx *ctx);
 
 #endif	/* CONFIG_DAMON_VADDR */
@@ -438,6 +440,8 @@ void damon_va_set_primitives(struct damon_ctx *ctx);
 void damon_pa_prepare_access_checks(struct damon_ctx *ctx);
 unsigned int damon_pa_check_accesses(struct damon_ctx *ctx);
 bool damon_pa_target_valid(void *t);
+int damon_pa_scheme_score(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme);
 void damon_pa_set_primitives(struct damon_ctx *ctx);
 
 #endif	/* CONFIG_DAMON_PADDR */
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 303db372e53b..99a579e8d046 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -121,6 +121,19 @@ int damon_pa_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
 	return 0;
 }
 
+int damon_pa_scheme_score(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme)
+{
+	switch (scheme->action) {
+	case DAMOS_PAGEOUT:
+		return damon_pageout_score(context, r, scheme);
+	default:
+		break;
+	}
+
+	return DAMOS_MAX_SCORE;
+}
+
 void damon_pa_set_primitives(struct damon_ctx *ctx)
 {
 	ctx->primitive.init = NULL;
@@ -131,4 +144,5 @@ void damon_pa_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.target_valid = damon_pa_target_valid;
 	ctx->primitive.cleanup = NULL;
 	ctx->primitive.apply_scheme = damon_pa_apply_scheme;
+	ctx->primitive.get_scheme_score = damon_pa_scheme_score;
 }
diff --git a/mm/damon/prmtv-common.c b/mm/damon/prmtv-common.c
index 01c1c1b37859..ca637a2bf7d8 100644
--- a/mm/damon/prmtv-common.c
+++ b/mm/damon/prmtv-common.c
@@ -236,3 +236,49 @@ bool damon_pa_young(unsigned long paddr, unsigned long *page_sz)
 	*page_sz = result.page_sz;
 	return result.accessed;
 }
+
+#define DAMON_MAX_SUBSCORE	(100)
+#define DAMON_MAX_AGE_IN_LOG	(32)
+
+int damon_pageout_score(struct damon_ctx *c, struct damon_region *r,
+			struct damos *s)
+{
+	unsigned int max_nr_accesses;
+	int freq_subscore;
+	unsigned int age_in_sec;
+	int age_in_log, age_subscore;
+	unsigned int freq_weight = s->limit.weight_nr_accesses;
+	unsigned int age_weight = s->limit.weight_age;
+	int hotness;
+
+	max_nr_accesses = c->aggr_interval / c->sample_interval;
+	freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses;
+
+	age_in_sec = (unsigned long)r->age * c->aggr_interval / 1000000;
+	for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
+			age_in_log++, age_in_sec >>= 1)
+		;
+
+	/* If frequency is 0, higher age means it's colder */
+	if (freq_subscore == 0)
+		age_in_log *= -1;
+
+	/*
+	 * Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
+	 * Scale it to be in [0, 100] and set it as age subscore.
+	 */
+	age_in_log += DAMON_MAX_AGE_IN_LOG;
+	age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
+		DAMON_MAX_AGE_IN_LOG / 2;
+
+	hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
+	if (freq_weight + age_weight)
+		hotness /= freq_weight + age_weight;
+	/*
+	 * Transform it to fit in [0, DAMOS_MAX_SCORE]
+	 */
+	hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
+
+	/* Return coldness of the region */
+	return DAMOS_MAX_SCORE - hotness;
+}
diff --git a/mm/damon/prmtv-common.h b/mm/damon/prmtv-common.h
index ba0c4eecbb79..b27c4e94917e 100644
--- a/mm/damon/prmtv-common.h
+++ b/mm/damon/prmtv-common.h
@@ -26,3 +26,6 @@ bool damon_va_young(struct mm_struct *mm, unsigned long addr,
 
 void damon_pa_mkold(unsigned long paddr);
 bool damon_pa_young(unsigned long paddr, unsigned long *page_sz);
+
+int damon_pageout_score(struct damon_ctx *c, struct damon_region *r,
+			struct damos *s);
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index de54ca70955d..cc70991076be 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -525,6 +525,20 @@ int damon_va_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
 	return damos_madvise(t, r, madv_action);
 }
 
+int damon_va_scheme_score(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme)
+{
+
+	switch (scheme->action) {
+	case DAMOS_PAGEOUT:
+		return damon_pageout_score(context, r, scheme);
+	default:
+		break;
+	}
+
+	return DAMOS_MAX_SCORE;
+}
+
 void damon_va_set_primitives(struct damon_ctx *ctx)
 {
 	ctx->primitive.init = damon_va_init;
@@ -535,6 +549,7 @@ void damon_va_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.target_valid = damon_va_target_valid;
 	ctx->primitive.cleanup = damon_va_cleanup;
 	ctx->primitive.apply_scheme = damon_va_apply_scheme;
+	ctx->primitive.get_scheme_score = damon_va_scheme_score;
 }
 
 #include "vaddr-test.h"
-- 
2.17.1