Re: [PATCH v3] mm: move pgscan, pgsteal, pgrefill to node stats

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

On 2/18/26 23:26, JP Kobryn (Meta) wrote:
> From: JP Kobryn <jp.kobryn@linux.dev>
> 
> There are situations where reclaim kicks in on a system with free memory.
> One possible cause is a NUMA imbalance scenario where one or more nodes are
> under pressure. It would help if we could easily identify such nodes.
> 
> Move the pgscan, pgsteal, and pgrefill counters from vm_event_item to
> node_stat_item to provide per-node reclaim visibility. With these counters
> as node stats, the values are now displayed in the per-node section of
> /proc/zoneinfo, which allows for quick identification of the affected
> nodes.
> 
> /proc/vmstat continues to report the same counters, aggregated across all
> nodes. But the ordering of these items within the readout changes as they
> move from the vm events section to the node stats section.
> 
> Memcg accounting of these counters is preserved. The relocated counters
> remain visible in memory.stat alongside the existing aggregate pgscan and
> pgsteal counters.
> 
> However, this change affects how the global counters are accumulated.
> Previously, the global event count update was gated on !cgroup_reclaim(),
> excluding memcg-based reclaim from /proc/vmstat. Now that
> mod_lruvec_state() is being used to update the counters, the global
> counters will include all reclaim. This is consistent with how pgdemote
> counters are already tracked.
> 
> Finally, the virtio_balloon driver is updated to use
> global_node_page_state() to fetch the counters, as they are no longer
> accessible through the vm_events array.
> 
> Signed-off-by: JP Kobryn <jp.kobryn@linux.dev>
> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>