1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Common Primitives for Data Access Monitoring
  4 *
  5 * Author: SeongJae Park <sj@kernel.org>
  6 */
  7
  8#include <linux/mmu_notifier.h>
  9#include <linux/page_idle.h>
 10#include <linux/pagemap.h>
 11#include <linux/rmap.h>
 12
 13#include "ops-common.h"
 14
 15/*
 16 * Get an online page for a pfn if it's in the LRU list.  Otherwise, returns
 17 * NULL.
 18 *
 19 * The body of this function is stolen from the 'page_idle_get_page()'.  We
 20 * steal rather than reuse it because the code is quite simple.
 21 */
 22struct page *damon_get_page(unsigned long pfn)
 23{
 24	struct page *page = pfn_to_online_page(pfn);
 25
 26	if (!page || !PageLRU(page) || !get_page_unless_zero(page))
 27		return NULL;
 28
 29	if (unlikely(!PageLRU(page))) {
 30		put_page(page);
 31		page = NULL;
 32	}
 33	return page;
 34}
 35
 36void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr)
 37{
 38	bool referenced = false;
 39	struct page *page = damon_get_page(pte_pfn(*pte));
 40
 41	if (!page)
 42		return;
 43
 44	if (pte_young(*pte)) {
 45		referenced = true;
 46		*pte = pte_mkold(*pte);
 47	}
 48
 49#ifdef CONFIG_MMU_NOTIFIER
 50	if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE))
 51		referenced = true;
 52#endif /* CONFIG_MMU_NOTIFIER */
 53
 54	if (referenced)
 55		set_page_young(page);
 56
 57	set_page_idle(page);
 58	put_page(page);
 59}
 60
 61void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr)
 62{
 63#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 64	bool referenced = false;
 65	struct page *page = damon_get_page(pmd_pfn(*pmd));
 66
 67	if (!page)
 68		return;
 69
 70	if (pmd_young(*pmd)) {
 71		referenced = true;
 72		*pmd = pmd_mkold(*pmd);
 73	}
 74
 75#ifdef CONFIG_MMU_NOTIFIER
 76	if (mmu_notifier_clear_young(mm, addr, addr + HPAGE_PMD_SIZE))
 77		referenced = true;
 78#endif /* CONFIG_MMU_NOTIFIER */
 79
 80	if (referenced)
 81		set_page_young(page);
 82
 83	set_page_idle(page);
 84	put_page(page);
 85#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 86}
 87
 88#define DAMON_MAX_SUBSCORE	(100)
 89#define DAMON_MAX_AGE_IN_LOG	(32)
 90
 91int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
 92			struct damos *s)
 93{
 94	unsigned int max_nr_accesses;
 95	int freq_subscore;
 96	unsigned int age_in_sec;
 97	int age_in_log, age_subscore;
 98	unsigned int freq_weight = s->quota.weight_nr_accesses;
 99	unsigned int age_weight = s->quota.weight_age;
100	int hotness;
101
102	max_nr_accesses = c->attrs.aggr_interval / c->attrs.sample_interval;
103	freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses;
104
105	age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
106	for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
107			age_in_log++, age_in_sec >>= 1)
108		;
109
110	/* If frequency is 0, higher age means it's colder */
111	if (freq_subscore == 0)
112		age_in_log *= -1;
113
114	/*
115	 * Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
116	 * Scale it to be in [0, 100] and set it as age subscore.
117	 */
118	age_in_log += DAMON_MAX_AGE_IN_LOG;
119	age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
120		DAMON_MAX_AGE_IN_LOG / 2;
121
122	hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
123	if (freq_weight + age_weight)
124		hotness /= freq_weight + age_weight;
125	/*
126	 * Transform it to fit in [0, DAMOS_MAX_SCORE]
127	 */
128	hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
129
130	return hotness;
131}
132
133int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
134			struct damos *s)
135{
136	int hotness = damon_hot_score(c, r, s);
137
138	/* Return coldness of the region */
139	return DAMOS_MAX_SCORE - hotness;
140}