[RFC PATCH v3 6/7] mm/damon/paddr: introduce DAMOS_MIGRATE_HOT action for promotion

Honggyu Kim
2024-04-05T06:09:18Z

From: Hyeongtak Ji <hyeongtak.ji@sk.com>

This patch introduces DAMOS_MIGRATE_HOT action, which is similar to
DAMOS_MIGRATE_COLD, but it is targeted to migrate hot pages.

It migrates pages inside the given region to the 'target_nid' NUMA node
in the sysfs.

Here is one of the example usage of this 'migrate_hot' action.

$ cd /sys/kernel/mm/damon/admin/kdamonds/<N>
$ cat contexts/<N>/schemes/<N>/action
migrate_hot
$ echo 0 > contexts/<N>/schemes/<N>/target_nid
$ echo commit > state
$ numactl -p 2 ./hot_cold 500M 600M &
$ numastat -c -p hot_cold

Per-node process memory usage (in MBs)
PID Node 0 Node 1 Node 2 Total
-------------- ------ ------ ------ -----
701 (hot_cold) 501 0 601 1101

Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
---
include/linux/damon.h | 2 ++
mm/damon/paddr.c | 12 ++++++++++--
mm/damon/sysfs-schemes.c | 4 +++-
3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index df8671e69a70..934c95a7c042 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -105,6 +105,7 @@ struct damon_target {
* @DAMOS_NOHUGEPAGE: Call ``madvise()`` for the region with MADV_NOHUGEPAGE.
* @DAMOS_LRU_PRIO: Prioritize the region on its LRU lists.
* @DAMOS_LRU_DEPRIO: Deprioritize the region on its LRU lists.
+ * @DAMOS_MIGRATE_HOT: Migrate for the given hot region.
* @DAMOS_MIGRATE_COLD: Migrate for the given cold region.
* @DAMOS_STAT: Do nothing but count the stat.
* @NR_DAMOS_ACTIONS: Total number of DAMOS actions
@@ -123,6 +124,7 @@ enum damos_action {
DAMOS_NOHUGEPAGE,
DAMOS_LRU_PRIO,
DAMOS_LRU_DEPRIO,
+ DAMOS_MIGRATE_HOT,
DAMOS_MIGRATE_COLD,
DAMOS_STAT, /* Do nothing but only record the stat */
NR_DAMOS_ACTIONS,
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index fe217a26f788..fd9d35b5cc83 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -229,6 +229,7 @@ static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)

enum migration_mode {
MIG_PAGEOUT,
+ MIG_MIGRATE_HOT,
MIG_MIGRATE_COLD,
};

@@ -375,8 +376,10 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
if (damos_pa_filter_out(s, folio))
goto put_folio;

- folio_clear_referenced(folio);
- folio_test_clear_young(folio);
+ if (mm != MIG_MIGRATE_HOT) {
+ folio_clear_referenced(folio);
+ folio_test_clear_young(folio);
+ }
if (!folio_isolate_lru(folio))
goto put_folio;
/*
@@ -394,6 +397,7 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
case MIG_PAGEOUT:
applied = reclaim_pages(&folio_list);
break;
+ case MIG_MIGRATE_HOT:
case MIG_MIGRATE_COLD:
applied = damon_pa_migrate_pages(&folio_list, mm,
s->target_nid);
@@ -454,6 +458,8 @@ static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
return damon_pa_mark_accessed(r, scheme);
case DAMOS_LRU_DEPRIO:
return damon_pa_deactivate_pages(r, scheme);
+ case DAMOS_MIGRATE_HOT:
+ return damon_pa_migrate(r, scheme, MIG_MIGRATE_HOT);
case DAMOS_MIGRATE_COLD:
return damon_pa_migrate(r, scheme, MIG_MIGRATE_COLD);
case DAMOS_STAT:
@@ -476,6 +482,8 @@ static int damon_pa_scheme_score(struct damon_ctx *context,
return damon_hot_score(context, r, scheme);
case DAMOS_LRU_DEPRIO:
return damon_cold_score(context, r, scheme);
+ case DAMOS_MIGRATE_HOT:
+ return damon_hot_score(context, r, scheme);
case DAMOS_MIGRATE_COLD:
return damon_cold_score(context, r, scheme);
default:
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 18b7d054c748..1d2f62aa79ca 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1406,6 +1406,7 @@ static const char * const damon_sysfs_damos_action_strs[] = {
"nohugepage",
"lru_prio",
"lru_deprio",
+ "migrate_hot",
"migrate_cold",
"stat",
};
@@ -1660,7 +1661,8 @@ static ssize_t target_nid_store(struct kobject *kobj,
struct damon_sysfs_scheme, kobj);
int err = 0;

- if (scheme->action != DAMOS_MIGRATE_COLD)
+ if (scheme->action != DAMOS_MIGRATE_HOT &&
+ scheme->action != DAMOS_MIGRATE_COLD)
return -EINVAL;

/* TODO: error handling for target_nid range. */
--
2.34.1