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

["JP Kobryn (Meta)" <inwardvessel@gmail.com>]

On 2/16/26 12:26 AM, Michal Hocko wrote:
> On Thu 12-02-26 13:22:56, JP Kobryn wrote:
>> On 2/11/26 11:29 PM, Michal Hocko wrote:
>>> On Wed 11-02-26 20:51:08, 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.
>>>
>>> Could you be more specific how exactly do you plan to use those
>>> counters?
>>
>> Yes. Patch 2 allows us to find which nodes are undergoing reclaim. Once
>> we identify the affected node(s), the new mpol counters (this patch)
>> allow us correlate the pressure to the mempolicy driving it.
> 
> I would appreciate somehow more specificity. You are adding counters
> that are not really easy to drop once they are in. Sure we have
> precedence of dropping some counters in the past so this is not as hard
> as usual userspace APIs but still...
> 
> How exactly do you tolerate mempolicy allocations to specific nodes?
> While MPOL_MBIND is quite straightforward others are less so.

The design does account for this regardless of the policy. In the call
to __mod_node_page_state(), I'm using page_pgdat(page) so the stat is
attributed to the node where the page actually landed.