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

[JP Kobryn <inwardvessel@gmail.com>]

On 2/12/26 7:07 AM, Shakeel Butt wrote:
> On Wed, Feb 11, 2026 at 08:51:08PM -0800, 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>
> 
> [...]
> 
>>   int mempolicy_set_node_perf(unsigned int node, struct access_coordinate *coords)
>>   {
>>   	struct weighted_interleave_state *new_wi_state, *old_wi_state = NULL;
>> @@ -2446,8 +2461,14 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order,
>>   
>>   	nodemask = policy_nodemask(gfp, pol, ilx, &nid);
>>   
>> -	if (pol->mode == MPOL_PREFERRED_MANY)
>> -		return alloc_pages_preferred_many(gfp, order, nid, nodemask);
>> +	if (pol->mode == MPOL_PREFERRED_MANY) {
>> +		page = alloc_pages_preferred_many(gfp, order, nid, nodemask);
>> +		if (page)
>> +			__mod_node_page_state(page_pgdat(page),
>> +					mpol_node_stat(MPOL_PREFERRED_MANY), 1 << order);
> 
> Here and two places below, please use mod_node_page_state() instead of
> __mod_node_page_state() as __foo() requires preempt disable or if the
> given stat can be updated in IRQ, then IRQ disable. This code path does
> not do either of that.

Thanks, I also see syzbot flagged this as well. I can make this change
in v2.