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// SPDX-License-Identifier: GPL-2.0
/*
* Common Primitives for Data Access Monitoring
*
* Author: SeongJae Park <sj@kernel.org>
*/
#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include "ops-common.h"
/*
* Get an online page for a pfn if it's in the LRU list. Otherwise, returns
* NULL.
*
* The body of this function is stolen from the 'page_idle_get_folio()'. We
* steal rather than reuse it because the code is quite simple.
*/
struct folio *damon_get_folio(unsigned long pfn)
{
struct page *page = pfn_to_online_page(pfn);
struct folio *folio;
if (!page)
return NULL;
folio = page_folio(page);
if (!folio_test_lru(folio) || !folio_try_get(folio))
return NULL;
if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
folio_put(folio);
folio = NULL;
}
return folio;
}
void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
{
pte_t pteval = ptep_get(pte);
struct folio *folio;
bool young = false;
unsigned long pfn;
if (likely(pte_present(pteval)))
pfn = pte_pfn(pteval);
else
pfn = swp_offset_pfn(pte_to_swp_entry(pteval));
folio = damon_get_folio(pfn);
if (!folio)
return;
/*
* PFN swap PTEs, such as device-exclusive ones, that actually map pages
* are "old" from a CPU perspective. The MMU notifier takes care of any
* device aspects.
*/
if (likely(pte_present(pteval)))
young |= ptep_test_and_clear_young(vma, addr, pte);
young |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
if (young)
folio_set_young(folio);
folio_set_idle(folio);
folio_put(folio);
}
void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
if (!folio)
return;
if (pmdp_clear_young_notify(vma, addr, pmd))
folio_set_young(folio);
folio_set_idle(folio);
folio_put(folio);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
}
#define DAMON_MAX_SUBSCORE (100)
#define DAMON_MAX_AGE_IN_LOG (32)
int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
struct damos *s)
{
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;
freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
damon_max_nr_accesses(&c->attrs);
age_in_sec = (unsigned long)r->age * c->attrs.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 hotness;
}
int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
struct damos *s)
{
int hotness = damon_hot_score(c, r, s);
/* Return coldness of the region */
return DAMOS_MAX_SCORE - hotness;
}
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