This patch introduces DAMOS_DEMOTE action, which is similar to
DAMOS_PAGEOUT, but demote folios instead of swapping them out.
Since there are some common routines with pageout, many functions have
similar logics between pageout and demote.
damon_pa_migrate_folio_list() is a minimized version of
shrink_folio_list(), but it's minified only for demotion.
Signed-off-by: Honggyu Kim <honggyu.kim@xxxxxx>
Signed-off-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
---
include/linux/damon.h | 2 +
mm/damon/paddr.c | 222 ++++++++++++++++++++++++++++++++++++++-
mm/damon/sysfs-schemes.c | 1 +
3 files changed, 224 insertions(+), 1 deletion(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h
index e00ddf1ed39c..86e66772766b 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_DEMOTE: Do demotion for the given region.
* @DAMOS_STAT: Do nothing but count the stat.
* @NR_DAMOS_ACTIONS: Total number of DAMOS actions
*
@@ -122,6 +123,7 @@ enum damos_action {
DAMOS_NOHUGEPAGE,
DAMOS_LRU_PRIO,
DAMOS_LRU_DEPRIO,
+ DAMOS_DEMOTE,
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 277a1c4d833c..23e37ce57202 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -12,6 +12,9 @@
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/swap.h>
+#include <linux/memory-tiers.h>
+#include <linux/migrate.h>
+#include <linux/mm_inline.h>
#include "../internal.h"
#include "ops-common.h"
@@ -226,8 +229,214 @@ static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)
enum migration_mode {
MIG_PAGEOUT,
+ MIG_DEMOTE,
};
+/*
+ * XXX: This is copied from demote_folio_list as renamed as migrate_folio_list.
+ * Take folios on @migrate_folios and attempt to migrate them to another node.
+ * Folios which are not migrated are left on @migrate_folios.
+ */
+static unsigned int migrate_folio_list(struct list_head *migrate_folios,
+ struct pglist_data *pgdat,
+ enum migration_mode mm)
+{
+ int target_nid = next_demotion_node(pgdat->node_id);
+ unsigned int nr_succeeded;
+ nodemask_t allowed_mask;
+
+ struct migration_target_control mtc = {
+ /*
+ * Allocate from 'node', or fail quickly and quietly.
+ * When this happens, 'page' will likely just be discarded
+ * instead of migrated.
+ */
+ .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN |
+ __GFP_NOMEMALLOC | GFP_NOWAIT,
+ .nid = target_nid,
+ .nmask = &allowed_mask
+ };
+
+ if (pgdat->node_id == target_nid || target_nid == NUMA_NO_NODE)
+ return 0;
+
+ if (list_empty(migrate_folios))
+ return 0;
+
+ node_get_allowed_targets(pgdat, &allowed_mask);
+
+ /* Migration ignores all cpuset and mempolicy settings */
+ migrate_pages(migrate_folios, alloc_migrate_folio, NULL,
+ (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
+ &nr_succeeded);
+
+ __count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
+
+ return nr_succeeded;
+}
+
+enum folio_references {
+ FOLIOREF_RECLAIM,
+ FOLIOREF_KEEP,
+ FOLIOREF_ACTIVATE,
+};
+
+/*
+ * XXX: This is just copied and simplified from folio_check_references at
+ * mm/vmscan.c but without having scan_control.
+ */
+static enum folio_references folio_check_references(struct folio *folio)
+{
+ int referenced_ptes, referenced_folio;
+ unsigned long vm_flags;
+
+ referenced_ptes = folio_referenced(folio, 1, NULL, &vm_flags);
+ referenced_folio = folio_test_clear_referenced(folio);
+
+ /* rmap lock contention: rotate */
+ if (referenced_ptes == -1)
+ return FOLIOREF_KEEP;
+
+ if (referenced_ptes) {
+ /*
+ * All mapped folios start out with page table
+ * references from the instantiating fault, so we need
+ * to look twice if a mapped file/anon folio is used more
+ * than once.
+ *
+ * Mark it and spare it for another trip around the
+ * inactive list. Another page table reference will
+ * lead to its activation.
+ *
+ * Note: the mark is set for activated folios as well
+ * so that recently deactivated but used folios are
+ * quickly recovered.
+ */
+ folio_set_referenced(folio);
+
+ if (referenced_folio || referenced_ptes > 1)
+ return FOLIOREF_ACTIVATE;
+
+ /*
+ * Activate file-backed executable folios after first usage.
+ */
+ if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio))
+ return FOLIOREF_ACTIVATE;
+
+ return FOLIOREF_KEEP;
+ }
+
+ return FOLIOREF_RECLAIM;
+}
+
+/*
+ * XXX: This is minimized implmentation based on shrink_folio_list only for
+ * the demotion calling demote_folio_list.
+ */
+static unsigned int damon_pa_migrate_folio_list(struct list_head *folio_list,
+ struct pglist_data *pgdat,
+ enum migration_mode mm)
+{
+ unsigned int nr_migrated = 0;
+ struct folio *folio;
+ LIST_HEAD(ret_folios);
+ LIST_HEAD(migrate_folios);
+
+ cond_resched();
+
+ while (!list_empty(folio_list)) {
+ struct folio *folio;
+ enum folio_references references;
+
+ cond_resched();
+
+ folio = lru_to_folio(folio_list);
+ list_del(&folio->lru);
+
+ if (!folio_trylock(folio))
+ goto keep;
+
+ VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
+
+ references = folio_check_references(folio);
+ if (references == FOLIOREF_KEEP)
+ goto keep_locked;
+
+ /* Relocate its contents to another node. */
+ list_add(&folio->lru, &migrate_folios);
+ folio_unlock(folio);
+ continue;
+keep_locked:
+ folio_unlock(folio);
+keep:
+ list_add(&folio->lru, &ret_folios);
+ VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
+ }
+ /* 'folio_list' is always empty here */
+
+ /* Migrate folios selected for migration */
+ nr_migrated += migrate_folio_list(&migrate_folios, pgdat, mm);
+ /* Folios that could not be migrated are still in @migrate_folios */
+ if (!list_empty(&migrate_folios)) {
+ /* Folios which weren't migrated go back on @folio_list */
+ list_splice_init(&migrate_folios, folio_list);
+ }
+
+ try_to_unmap_flush();
+
+ list_splice(&ret_folios, folio_list);
+
+ while (!list_empty(folio_list)) {
+ folio = lru_to_folio(folio_list);
+ list_del(&folio->lru);
+ folio_putback_lru(folio);
+ }
+
+ return nr_migrated;
+}
+
+/*
+ * XXX: This is almost identical to reclaim_pages() in mm/vmscan.c, but it
+ * internally calls damon_pa_migrate_folio_list() instead of
+ * reclaim_folio_list(). We might be better to think if we can have a
+ * common function for both cases.
+ */
+static unsigned long damon_pa_migrate_pages(struct list_head *folio_list,
+ enum migration_mode mm)
+{
+ int nid;
+ unsigned int nr_migrated = 0;
+ LIST_HEAD(node_folio_list);
+ unsigned int noreclaim_flag;
+
+ if (list_empty(folio_list))
+ return nr_migrated;
+
+ noreclaim_flag = memalloc_noreclaim_save();
+
+ nid = folio_nid(lru_to_folio(folio_list));
+ do {
+ struct folio *folio = lru_to_folio(folio_list);
+
+ if (nid == folio_nid(folio)) {
+ folio_clear_active(folio);
+ list_move(&folio->lru, &node_folio_list);
+ continue;
+ }
+
+ nr_migrated += damon_pa_migrate_folio_list(&node_folio_list,
+ NODE_DATA(nid), mm);
+ nid = folio_nid(lru_to_folio(folio_list));
+ } while (!list_empty(folio_list));
+
+ nr_migrated += damon_pa_migrate_folio_list(&node_folio_list,
+ NODE_DATA(nid), mm);
+
+ memalloc_noreclaim_restore(noreclaim_flag);
+
+ return nr_migrated;
+}
+
static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
enum migration_mode mm)
{
@@ -247,7 +456,11 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
folio_test_clear_young(folio);
if (!folio_isolate_lru(folio))
goto put_folio;
- if (folio_test_unevictable(folio))
+ /*
+ * Since unevictable folios can be demoted or promoted,
+ * unevictable test is needed only for pageout.
+ */
+ if (mm == MIG_PAGEOUT && folio_test_unevictable(folio))
folio_putback_lru(folio);
else
list_add(&folio->lru, &folio_list);
@@ -258,6 +471,9 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
case MIG_PAGEOUT:
applied = reclaim_pages(&folio_list);
break;
+ case MIG_DEMOTE:
+ applied = damon_pa_migrate_pages(&folio_list, mm);
+ break;
default:
/* Unexpected migration mode. */
return 0;
@@ -314,6 +530,8 @@ 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_DEMOTE:
+ return damon_pa_migrate(r, scheme, MIG_DEMOTE);
case DAMOS_STAT:
break;
default:
@@ -334,6 +552,8 @@ 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_DEMOTE:
+ return damon_cold_score(context, r, scheme);
default:
break;
}
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index fe0fe2562000..53e47fad5021 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1186,6 +1186,7 @@ static const char * const damon_sysfs_damos_action_strs[] = {
"nohugepage",
"lru_prio",
"lru_deprio",
+ "demote",
"stat",
};
--
2.34.1
