Re: [PATCH v2] mm: move pgscan and pgsteal to node stats

["JP Kobryn (Meta)" <jp.kobryn@linux.dev>]

On 2/18/26 12:54 AM, Vlastimil Babka (SUSE) wrote:
> On 2/18/26 04:29, 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 and pgsteal 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.
> 
> Hm so that leaves PGREFILL (scanned in the active list) the odd one out,
> right? Not being per-node and gated on !cgroup_reclaim() for global stats.
> Should we change it too for full consistency?

I'm fine with adding coverage for the active list side as well. For
completeness, I could also include PGDEACTIVATE.