Re: [RFC PATCH 4/4] mm/damon: introduce DAMOS_PROMOTE action for promotion

SeongJae Park
2024-01-16T20:32:35Z

On Mon, 15 Jan 2024 13:52:52 +0900 Honggyu Kim <honggyu.kim@sk.com> wrote:

> From: Hyeongtak Ji <hyeongtak.ji@sk.com>
>
> This patch introduces DAMOS_PROMOTE action for paddr mode.
>
> It includes renaming alloc_demote_folio to alloc_migrate_folio to use it
> for promotion as well.
>
> The execution sequence of DAMOS_DEMOTE and DAMOS_PROMOTE look as
> follows for comparison.
>
> DAMOS_DEMOTE action
> damo_pa_apply_scheme
> -> damon_pa_reclaim
> -> demote_pages
> -> do_demote_folio_list
> -> __demote_folio_list
> -> demote_folio_list
>
> DAMOS_PROMOTE action
> damo_pa_apply_scheme
> -> damon_pa_promote
> -> promote_pages
> -> do_promote_folio_list
> -> __promote_folio_list
> -> promote_folio_list
>
> Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
> Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
> ---
> include/linux/damon.h | 2 +
> include/linux/migrate_mode.h | 1 +
> include/linux/vm_event_item.h | 1 +
> include/trace/events/migrate.h | 3 +-
> mm/damon/paddr.c | 29 ++++++++
> mm/damon/sysfs-schemes.c | 1 +
> mm/internal.h | 1 +
> mm/vmscan.c | 129 ++++++++++++++++++++++++++++++++-
> mm/vmstat.c | 1 +
> 9 files changed, 165 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index 4c0a0fef09c5..477060bb6718 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -107,6 +107,7 @@ struct damon_target {
> * @DAMOS_LRU_DEPRIO: Deprioritize the region on its LRU lists.
> * @DAMOS_STAT: Do nothing but count the stat.
> * @DAMOS_DEMOTE: Do demotion for the current region.
> + * @DAMOS_PROMOTE: Do promotion if possible, otherwise do nothing.

Like LRU_PRIO is defined before LRU_DEPRIO, what about defining PROMOTE before
DEMOTE?

> * @NR_DAMOS_ACTIONS: Total number of DAMOS actions
> *
> * The support of each action is up to running &struct damon_operations.
> @@ -125,6 +126,7 @@ enum damos_action {
> DAMOS_LRU_DEPRIO,
> DAMOS_STAT, /* Do nothing but only record the stat */
> DAMOS_DEMOTE,
> + DAMOS_PROMOTE,
> NR_DAMOS_ACTIONS,
> };
>
> diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
> index f37cc03f9369..63f75eb9abf3 100644
> --- a/include/linux/migrate_mode.h
> +++ b/include/linux/migrate_mode.h
> @@ -29,6 +29,7 @@ enum migrate_reason {
> MR_CONTIG_RANGE,
> MR_LONGTERM_PIN,
> MR_DEMOTION,
> + MR_PROMOTION,
> MR_TYPES
> };
>
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index 8abfa1240040..63cf920afeaa 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -44,6 +44,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> PGDEMOTE_KSWAPD,
> PGDEMOTE_DIRECT,
> PGDEMOTE_KHUGEPAGED,
> + PGPROMOTE,
> PGSCAN_KSWAPD,
> PGSCAN_DIRECT,
> PGSCAN_KHUGEPAGED,
> diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
> index 0190ef725b43..f0dd569c1e62 100644
> --- a/include/trace/events/migrate.h
> +++ b/include/trace/events/migrate.h
> @@ -22,7 +22,8 @@
> EM( MR_NUMA_MISPLACED, "numa_misplaced") \
> EM( MR_CONTIG_RANGE, "contig_range") \
> EM( MR_LONGTERM_PIN, "longterm_pin") \
> - EMe(MR_DEMOTION, "demotion")
> + EM( MR_DEMOTION, "demotion") \
> + EMe(MR_PROMOTION, "promotion")
>
> /*
> * First define the enums in the above macros to be exported to userspace
> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
> index d3e3f077cd00..360ce69d5898 100644
> --- a/mm/damon/paddr.c
> +++ b/mm/damon/paddr.c
> @@ -257,6 +257,32 @@ static unsigned long damon_pa_reclaim(struct damon_region *r, struct damos *s, b
> return applied * PAGE_SIZE;
> }
>
> +static unsigned long damon_pa_promote(struct damon_region *r, struct damos *s)
> +{
> + unsigned long addr, applied;
> + LIST_HEAD(folio_list);
> +
> + for (addr = r->ar.start; addr < r->ar.end; addr += PAGE_SIZE) {
> + struct folio *folio = damon_get_folio(PHYS_PFN(addr));
> +
> + if (!folio)
> + continue;
> +
> + if (damos_pa_filter_out(s, folio))
> + goto put_folio;
> +
> + if (!folio_isolate_lru(folio))
> + goto put_folio;
> +
> + list_add(&folio->lru, &folio_list);
> +put_folio:
> + folio_put(folio);
> + }
> + applied = promote_pages(&folio_list);
> + cond_resched();
> + return applied * PAGE_SIZE;
> +}
> +
> static inline unsigned long damon_pa_mark_accessed_or_deactivate(
> struct damon_region *r, struct damos *s, bool mark_accessed)
> {
> @@ -309,6 +335,8 @@ static unsigned long damon_pa_apply_scheme(struct damon_ctx *ctx,
> break;
> case DAMOS_DEMOTE:
> return damon_pa_reclaim(r, scheme, true);
> + case DAMOS_PROMOTE:
> + return damon_pa_promote(r, scheme);
> default:
> /* DAMOS actions that not yet supported by 'paddr'. */
> break;
> @@ -326,6 +354,7 @@ static int damon_pa_scheme_score(struct damon_ctx *context,
> case DAMOS_DEMOTE:
> return damon_cold_score(context, r, scheme);
> case DAMOS_LRU_PRIO:
> + case DAMOS_PROMOTE:
> return damon_hot_score(context, r, scheme);

As mentioned on the previous patch, I'd prefer keeping the order of operations
and having dedicated branches for each operation.

> default:
> break;
> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index ac7cd3f17b12..1b84d0af7e1f 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c
> @@ -1188,6 +1188,7 @@ static const char * const damon_sysfs_damos_action_strs[] = {
> "lru_deprio",
> "stat",
> "demote",
> + "promote",
> };
>
> static struct damon_sysfs_scheme *damon_sysfs_scheme_alloc(
> diff --git a/mm/internal.h b/mm/internal.h
> index 2380397ec2f3..f159455e63d4 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -870,6 +870,7 @@ unsigned long reclaim_pages(struct list_head *folio_list);
> unsigned int reclaim_clean_pages_from_list(struct zone *zone,
> struct list_head *folio_list);
> unsigned long demote_pages(struct list_head *folio_list);
> +unsigned long promote_pages(struct list_head *folio_list);
> /* The ALLOC_WMARK bits are used as an index to zone->watermark */
> #define ALLOC_WMARK_MIN WMARK_MIN
> #define ALLOC_WMARK_LOW WMARK_LOW
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index eaa3dd6b7562..f03be320f9ad 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -910,7 +910,7 @@ static void folio_check_dirty_writeback(struct folio *folio,
> mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
> }
>
> -static struct folio *alloc_demote_folio(struct folio *src,
> +static struct folio *alloc_migrate_folio(struct folio *src,
> unsigned long private)

As also mentioned on the previous patch, I'm unsure if vmscan.c is the right
place for general migration.

> {
> struct folio *dst;
> @@ -973,7 +973,7 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
> node_get_allowed_targets(pgdat, &allowed_mask);
>
> /* Demotion ignores all cpuset and mempolicy settings */
> - migrate_pages(demote_folios, alloc_demote_folio, NULL,
> + migrate_pages(demote_folios, alloc_migrate_folio, NULL,
> (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
> &nr_succeeded);
>
> @@ -982,6 +982,48 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
> return nr_succeeded;
> }
>
> +/*
> + * Take folios on @promote_folios and attempt to promote them to another node.
> + * Folios which are not promoted are left on @promote_folios.
> + */
> +static unsigned int promote_folio_list(struct list_head *promote_folios,
> + struct pglist_data *pgdat)
> +{
> + int target_nid = next_promotion_node(pgdat->node_id);
> + unsigned int nr_succeeded;
> + nodemask_t allowed_mask = NODE_MASK_NONE;
> +
> + struct migration_target_control mtc = {
> + /*
> + * Allocate from 'node', or fail quickly and quietly.
> + * When this happens, 'page' will likely be stayed
> + * 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)
> + return 0;
> +
> + if (list_empty(promote_folios))
> + return 0;
> +
> + if (target_nid == NUMA_NO_NODE)
> + return 0;
> +
> + /* Promotion ignores all cpuset and mempolicy settings */
> + migrate_pages(promote_folios, alloc_migrate_folio, NULL,
> + (unsigned long)&mtc, MIGRATE_ASYNC, MR_PROMOTION,
> + &nr_succeeded);
> +
> + __count_vm_events(PGPROMOTE, nr_succeeded);
> +
> + return nr_succeeded;
> +}
> +
> static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask)
> {
> if (gfp_mask & __GFP_FS)
> @@ -1058,6 +1100,65 @@ static unsigned int __demote_folio_list(struct list_head *folio_list,
> return nr_demoted;
> }
>
> +/*
> + * __promote_folio_list() returns the number of promoted pages
> + */
> +static unsigned int __promote_folio_list(struct list_head *folio_list,
> + struct pglist_data *pgdat, struct scan_control *sc)
> +{
> + LIST_HEAD(ret_folios);
> + LIST_HEAD(promote_folios);
> + unsigned int nr_promoted = 0;
> +
> + 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, sc);
> + if (references == FOLIOREF_KEEP ||
> + references == FOLIOREF_RECLAIM ||
> + references == FOLIOREF_RECLAIM_CLEAN)
> + goto keep_locked;
> +
> + /* Relocate its contents to another node. */
> + list_add(&folio->lru, &promote_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 promotion */
> + nr_promoted += promote_folio_list(&promote_folios, pgdat);

Again as mentioned on the previous patch, I was thinking promote_folios_list()
may call __promote_folio_list(). Making the __ prefix usage consistent with
other functions might be better, in my opinion.

> + /* Folios that could not be promoted are still in @promote_folios */
> + if (!list_empty(&promote_folios)) {
> + /* Folios which weren't promoted go back on @folio_list */
> + list_splice_init(&promote_folios, folio_list);
> + }
> +
> + try_to_unmap_flush();
> +
> + list_splice(&ret_folios, folio_list);
> +
> + return nr_promoted;
> +}
> +
> /*
> * shrink_folio_list() returns the number of reclaimed pages
> */
> @@ -2186,6 +2287,25 @@ static unsigned int do_demote_folio_list(struct list_head *folio_list,
> return nr_demoted;
> }
>
> +static unsigned int do_promote_folio_list(struct list_head *folio_list,
> + struct pglist_data *pgdat)
> +{
> + unsigned int nr_promoted;
> + struct folio *folio;
> + struct scan_control sc = {
> + .gfp_mask = GFP_KERNEL,
> + };
> +
> + nr_promoted = __promote_folio_list(folio_list, pgdat, &sc);
> + while (!list_empty(folio_list)) {
> + folio = lru_to_folio(folio_list);
> + list_del(&folio->lru);
> + folio_putback_lru(folio);
> + }
> +
> + return nr_promoted;
> +}
> +
> static unsigned long reclaim_or_migrate_folios(struct list_head *folio_list,
> unsigned int (*handler)(struct list_head *, struct pglist_data *))
> {
> @@ -2230,6 +2350,11 @@ unsigned long demote_pages(struct list_head *folio_list)
> return reclaim_or_migrate_folios(folio_list, do_demote_folio_list);
> }
>
> +unsigned long promote_pages(struct list_head *folio_list)
> +{
> + return reclaim_or_migrate_folios(folio_list, do_promote_folio_list);
> +}
> +
> static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
> struct lruvec *lruvec, struct scan_control *sc)
> {
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 359460deb377..c703abdb8137 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1282,6 +1282,7 @@ const char * const vmstat_text[] = {
> "pgdemote_kswapd",
> "pgdemote_direct",
> "pgdemote_khugepaged",
> + "pgpromote",
> "pgscan_kswapd",
> "pgscan_direct",
> "pgscan_khugepaged",
> --
> 2.34.1