Re: [PATCH 1/2] mm/mempolicy: track page allocations per mempolicy

[JP Kobryn <inwardvessel@gmail.com>]

On 2/12/26 7:24 AM, Vlastimil Babka wrote:
> On 2/12/26 05:51, JP Kobryn wrote:
>> It would be useful to see a breakdown of allocations to understand which
>> NUMA policies are driving them. For example, when investigating memory
>> pressure, having policy-specific counts could show that allocations were
>> bound to the affected node (via MPOL_BIND).
>>
>> Add per-policy page allocation counters as new node stat items. These
>> counters can provide correlation between a mempolicy and pressure on a
>> given node.
>>
>> Signed-off-by: JP Kobryn <inwardvessel@gmail.com>
>> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> 
> Are the numa_{hit,miss,etc.} counters insufficient? Could they be extended
> in a way that would capture any missing important details? A counter per
> policy type seems exhaustive, but then on one hand it might be not important
> to distinguish beetween some of them, and on the other hand it doesn't track
> the nodemask anyway.

The two patches of the series should complement each other. When
investigating memory pressure, we could identify the affected nodes
(patch 2). Then we can cross-reference the policy-specific stats to find
any correlation (this patch).

I think extending numa_* counters would call for more permutations to
account for the numa stat per policy. I think distinguishing between
MPOL_DEFAULT and MPOL_BIND is meaningful, for example. Am I
understanding your question?