mm/damon/vaddr,paddr: support pageout prioritization

This 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.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: SeongJae Park <[email protected]>
Cc: Amit Shah <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Leonard Foerster <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Markus Boehme <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/damon.h

@@ -421,6 +421,8 @@ 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 */
@@ -433,6 +435,8 @@ unsigned int damon_pa_check_accesses(struct damon_ctx *ctx);
 bool damon_pa_target_valid(void *t);
 int damon_pa_apply_scheme(struct damon_ctx *context, struct damon_target *t,
 		struct damon_region *r, struct damos *scheme);
+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 */

mm/damon/paddr.c

@@ -246,6 +246,19 @@ 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;
@@ -256,4 +269,5 @@ 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;
 }

mm/damon/prmtv-common.c

@@ -85,3 +85,49 @@ void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr)
 	put_page(page);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 }
+
+#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->quota.weight_nr_accesses;
+	unsigned int age_weight = s->quota.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;
+}

mm/damon/prmtv-common.h

@@ -15,3 +15,6 @@ struct page *damon_get_page(unsigned long pfn);
 
 void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr);
 void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr);
+
+int damon_pageout_score(struct damon_ctx *c, struct damon_region *r,
+			struct damos *s);

mm/damon/vaddr.c

@@ -633,6 +633,20 @@ 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;
@@ -643,6 +657,7 @@ void damon_va_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.target_valid = damon_va_target_valid;
 	ctx->primitive.cleanup = NULL;
 	ctx->primitive.apply_scheme = damon_va_apply_scheme;
+	ctx->primitive.get_scheme_score = damon_va_scheme_score;
 }
 
 #include "vaddr-test.h"