Re: [PATCH 2/2] mm: move pgscan and pgsteal to node stats

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 11, 2026 at 08:51:09PM -0800, JP Kobryn wrote:
> It would be useful to narrow down reclaim to specific nodes.
> 
> Provide per-node reclaim visibility by changing the pgscan and pgsteal
> stats from global vm_event_item's to node_stat_item's. Note this change has
> the side effect of now tracking these stats on a per-memcg basis.
> 
> Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>

virtio_balloon changes

> ---
>  drivers/virtio/virtio_balloon.c |  8 ++++----
>  include/linux/mmzone.h          | 12 +++++++++++
>  include/linux/vm_event_item.h   | 12 -----------
>  mm/memcontrol.c                 | 36 ++++++++++++++++++---------------
>  mm/vmscan.c                     | 32 +++++++++++------------------
>  mm/vmstat.c                     | 24 +++++++++++-----------
>  6 files changed, 60 insertions(+), 64 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 74fe59f5a78c..1341d9d1a2a1 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -374,13 +374,13 @@ static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_ALLOC_STALL, stall);
>  
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_SCAN,
> -		    pages_to_bytes(events[PGSCAN_KSWAPD]));
> +		    pages_to_bytes(global_node_page_state(PGSCAN_KSWAPD)));
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_SCAN,
> -		    pages_to_bytes(events[PGSCAN_DIRECT]));
> +		    pages_to_bytes(global_node_page_state(PGSCAN_DIRECT)));
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_RECLAIM,
> -		    pages_to_bytes(events[PGSTEAL_KSWAPD]));
> +		    pages_to_bytes(global_node_page_state(PGSTEAL_KSWAPD)));
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_RECLAIM,
> -		    pages_to_bytes(events[PGSTEAL_DIRECT]));
> +		    pages_to_bytes(global_node_page_state(PGSTEAL_DIRECT)));
>  
>  #ifdef CONFIG_HUGETLB_PAGE
>  	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 762609d5f0af..fc39c107a4b5 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -255,6 +255,18 @@ enum node_stat_item {
>  	PGDEMOTE_DIRECT,
>  	PGDEMOTE_KHUGEPAGED,
>  	PGDEMOTE_PROACTIVE,
> +	PGSTEAL_KSWAPD,
> +	PGSTEAL_DIRECT,
> +	PGSTEAL_KHUGEPAGED,
> +	PGSTEAL_PROACTIVE,
> +	PGSTEAL_ANON,
> +	PGSTEAL_FILE,
> +	PGSCAN_KSWAPD,
> +	PGSCAN_DIRECT,
> +	PGSCAN_KHUGEPAGED,
> +	PGSCAN_PROACTIVE,
> +	PGSCAN_ANON,
> +	PGSCAN_FILE,
>  #ifdef CONFIG_NUMA
>  	PGALLOC_MPOL_DEFAULT,
>  	PGALLOC_MPOL_PREFERRED,
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index 92f80b4d69a6..6f1787680658 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -40,19 +40,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  		PGLAZYFREED,
>  		PGREFILL,
>  		PGREUSE,
> -		PGSTEAL_KSWAPD,
> -		PGSTEAL_DIRECT,
> -		PGSTEAL_KHUGEPAGED,
> -		PGSTEAL_PROACTIVE,
> -		PGSCAN_KSWAPD,
> -		PGSCAN_DIRECT,
> -		PGSCAN_KHUGEPAGED,
> -		PGSCAN_PROACTIVE,
>  		PGSCAN_DIRECT_THROTTLE,
> -		PGSCAN_ANON,
> -		PGSCAN_FILE,
> -		PGSTEAL_ANON,
> -		PGSTEAL_FILE,
>  #ifdef CONFIG_NUMA
>  		PGSCAN_ZONE_RECLAIM_SUCCESS,
>  		PGSCAN_ZONE_RECLAIM_FAILED,
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 86f43b7e5f71..bde0b6536be6 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -328,6 +328,18 @@ static const unsigned int memcg_node_stat_items[] = {
>  	PGDEMOTE_DIRECT,
>  	PGDEMOTE_KHUGEPAGED,
>  	PGDEMOTE_PROACTIVE,
> +	PGSTEAL_KSWAPD,
> +	PGSTEAL_DIRECT,
> +	PGSTEAL_KHUGEPAGED,
> +	PGSTEAL_PROACTIVE,
> +	PGSTEAL_ANON,
> +	PGSTEAL_FILE,
> +	PGSCAN_KSWAPD,
> +	PGSCAN_DIRECT,
> +	PGSCAN_KHUGEPAGED,
> +	PGSCAN_PROACTIVE,
> +	PGSCAN_ANON,
> +	PGSCAN_FILE,
>  #ifdef CONFIG_HUGETLB_PAGE
>  	NR_HUGETLB,
>  #endif
> @@ -441,14 +453,6 @@ static const unsigned int memcg_vm_event_stat[] = {
>  #endif
>  	PSWPIN,
>  	PSWPOUT,
> -	PGSCAN_KSWAPD,
> -	PGSCAN_DIRECT,
> -	PGSCAN_KHUGEPAGED,
> -	PGSCAN_PROACTIVE,
> -	PGSTEAL_KSWAPD,
> -	PGSTEAL_DIRECT,
> -	PGSTEAL_KHUGEPAGED,
> -	PGSTEAL_PROACTIVE,
>  	PGFAULT,
>  	PGMAJFAULT,
>  	PGREFILL,
> @@ -1496,15 +1500,15 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>  
>  	/* Accumulated memory events */
>  	seq_buf_printf(s, "pgscan %lu\n",
> -		       memcg_events(memcg, PGSCAN_KSWAPD) +
> -		       memcg_events(memcg, PGSCAN_DIRECT) +
> -		       memcg_events(memcg, PGSCAN_PROACTIVE) +
> -		       memcg_events(memcg, PGSCAN_KHUGEPAGED));
> +		       memcg_page_state(memcg, PGSCAN_KSWAPD) +
> +		       memcg_page_state(memcg, PGSCAN_DIRECT) +
> +		       memcg_page_state(memcg, PGSCAN_PROACTIVE) +
> +		       memcg_page_state(memcg, PGSCAN_KHUGEPAGED));
>  	seq_buf_printf(s, "pgsteal %lu\n",
> -		       memcg_events(memcg, PGSTEAL_KSWAPD) +
> -		       memcg_events(memcg, PGSTEAL_DIRECT) +
> -		       memcg_events(memcg, PGSTEAL_PROACTIVE) +
> -		       memcg_events(memcg, PGSTEAL_KHUGEPAGED));
> +		       memcg_page_state(memcg, PGSTEAL_KSWAPD) +
> +		       memcg_page_state(memcg, PGSTEAL_DIRECT) +
> +		       memcg_page_state(memcg, PGSTEAL_PROACTIVE) +
> +		       memcg_page_state(memcg, PGSTEAL_KHUGEPAGED));
>  
>  	for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++) {
>  #ifdef CONFIG_MEMCG_V1
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 614ccf39fe3f..16a0f21e3ea1 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1977,7 +1977,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  	unsigned long nr_taken;
>  	struct reclaim_stat stat;
>  	bool file = is_file_lru(lru);
> -	enum vm_event_item item;
> +	enum node_stat_item item;
>  	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
>  	bool stalled = false;
>  
> @@ -2003,10 +2003,8 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  
>  	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
>  	item = PGSCAN_KSWAPD + reclaimer_offset(sc);
> -	if (!cgroup_reclaim(sc))
> -		__count_vm_events(item, nr_scanned);
> -	count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
> -	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
> +	mod_lruvec_state(lruvec, item, nr_scanned);
> +	mod_lruvec_state(lruvec, PGSCAN_ANON + file, nr_scanned);
>  
>  	spin_unlock_irq(&lruvec->lru_lock);
>  
> @@ -2023,10 +2021,8 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  					stat.nr_demoted);
>  	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
>  	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
> -	if (!cgroup_reclaim(sc))
> -		__count_vm_events(item, nr_reclaimed);
> -	count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
> -	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
> +	mod_lruvec_state(lruvec, item, nr_reclaimed);
> +	mod_lruvec_state(lruvec, PGSTEAL_ANON + file, nr_reclaimed);
>  
>  	lru_note_cost_unlock_irq(lruvec, file, stat.nr_pageout,
>  					nr_scanned - nr_reclaimed);
> @@ -4536,7 +4532,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>  {
>  	int i;
>  	int gen;
> -	enum vm_event_item item;
> +	enum node_stat_item item;
>  	int sorted = 0;
>  	int scanned = 0;
>  	int isolated = 0;
> @@ -4595,13 +4591,11 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>  	}
>  
>  	item = PGSCAN_KSWAPD + reclaimer_offset(sc);
> -	if (!cgroup_reclaim(sc)) {
> -		__count_vm_events(item, isolated);
> +	if (!cgroup_reclaim(sc))
>  		__count_vm_events(PGREFILL, sorted);
> -	}
> -	count_memcg_events(memcg, item, isolated);
> +	mod_lruvec_state(lruvec, item, isolated);
>  	count_memcg_events(memcg, PGREFILL, sorted);
> -	__count_vm_events(PGSCAN_ANON + type, isolated);
> +	mod_lruvec_state(lruvec, PGSCAN_ANON + type, isolated);
>  	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, scan_batch,
>  				scanned, skipped, isolated,
>  				type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
> @@ -4686,7 +4680,7 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>  	LIST_HEAD(clean);
>  	struct folio *folio;
>  	struct folio *next;
> -	enum vm_event_item item;
> +	enum node_stat_item item;
>  	struct reclaim_stat stat;
>  	struct lru_gen_mm_walk *walk;
>  	bool skip_retry = false;
> @@ -4750,10 +4744,8 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>  					stat.nr_demoted);
>  
>  	item = PGSTEAL_KSWAPD + reclaimer_offset(sc);
> -	if (!cgroup_reclaim(sc))
> -		__count_vm_events(item, reclaimed);
> -	count_memcg_events(memcg, item, reclaimed);
> -	__count_vm_events(PGSTEAL_ANON + type, reclaimed);
> +	mod_lruvec_state(lruvec, item, reclaimed);
> +	mod_lruvec_state(lruvec, PGSTEAL_ANON + type, reclaimed);
>  
>  	spin_unlock_irq(&lruvec->lru_lock);
>  
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 74e0ddde1e93..e4b259989d58 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1291,6 +1291,18 @@ const char * const vmstat_text[] = {
>  	[I(PGDEMOTE_DIRECT)]			= "pgdemote_direct",
>  	[I(PGDEMOTE_KHUGEPAGED)]		= "pgdemote_khugepaged",
>  	[I(PGDEMOTE_PROACTIVE)]			= "pgdemote_proactive",
> +	[I(PGSTEAL_KSWAPD)]			= "pgsteal_kswapd",
> +	[I(PGSTEAL_DIRECT)]			= "pgsteal_direct",
> +	[I(PGSTEAL_KHUGEPAGED)]			= "pgsteal_khugepaged",
> +	[I(PGSTEAL_PROACTIVE)]			= "pgsteal_proactive",
> +	[I(PGSTEAL_ANON)]			= "pgsteal_anon",
> +	[I(PGSTEAL_FILE)]			= "pgsteal_file",
> +	[I(PGSCAN_KSWAPD)]			= "pgscan_kswapd",
> +	[I(PGSCAN_DIRECT)]			= "pgscan_direct",
> +	[I(PGSCAN_KHUGEPAGED)]			= "pgscan_khugepaged",
> +	[I(PGSCAN_PROACTIVE)]			= "pgscan_proactive",
> +	[I(PGSCAN_ANON)]			= "pgscan_anon",
> +	[I(PGSCAN_FILE)]			= "pgscan_file",
>  #ifdef CONFIG_NUMA
>  	[I(PGALLOC_MPOL_DEFAULT)]		= "pgalloc_mpol_default",
>  	[I(PGALLOC_MPOL_PREFERRED)]		= "pgalloc_mpol_preferred",
> @@ -1344,19 +1356,7 @@ const char * const vmstat_text[] = {
>  
>  	[I(PGREFILL)]				= "pgrefill",
>  	[I(PGREUSE)]				= "pgreuse",
> -	[I(PGSTEAL_KSWAPD)]			= "pgsteal_kswapd",
> -	[I(PGSTEAL_DIRECT)]			= "pgsteal_direct",
> -	[I(PGSTEAL_KHUGEPAGED)]			= "pgsteal_khugepaged",
> -	[I(PGSTEAL_PROACTIVE)]			= "pgsteal_proactive",
> -	[I(PGSCAN_KSWAPD)]			= "pgscan_kswapd",
> -	[I(PGSCAN_DIRECT)]			= "pgscan_direct",
> -	[I(PGSCAN_KHUGEPAGED)]			= "pgscan_khugepaged",
> -	[I(PGSCAN_PROACTIVE)]			= "pgscan_proactive",
>  	[I(PGSCAN_DIRECT_THROTTLE)]		= "pgscan_direct_throttle",
> -	[I(PGSCAN_ANON)]			= "pgscan_anon",
> -	[I(PGSCAN_FILE)]			= "pgscan_file",
> -	[I(PGSTEAL_ANON)]			= "pgsteal_anon",
> -	[I(PGSTEAL_FILE)]			= "pgsteal_file",
>  
>  #ifdef CONFIG_NUMA
>  	[I(PGSCAN_ZONE_RECLAIM_SUCCESS)]	= "zone_reclaim_success",
> -- 
> 2.47.3