Re: [RFC PATCH v4 4/7] mm/demotion/dax/kmem: Set node's memory tier to MEMORY_TIER_PMEM

Bharata B Rao
2022-06-02T06:36:51Z

On 6/1/2022 7:19 PM, Aneesh Kumar K V wrote:
> On 6/1/22 11:59 AM, Bharata B Rao wrote:
>> I was experimenting with this patchset and found this behaviour.
>> Here's what I did:
>>
>> Boot a KVM guest with vNVDIMM device which ends up with device_dax
>> driver by default.
>>
>> Use it as RAM by binding it to dax kmem driver. It now appears as
>> RAM with a new NUMA node that is put to memtier1 (the existing tier
>> where DRAM already exists)
>>
>
> That should have placed it in memtier2.
>
>> I can move it to memtier2 (MEMORY_RANK_PMEM) manually, but isn't
>> that expected to happen automatically when a node with dax kmem
>> device comes up?
>>
>
> This can happen if we have added the same NUMA node to memtier1 before dax kmem driver initialized the pmem memory. Can you check before the above node_set_memory_tier_rank() whether the specific NUMA node is already part of any memory tier?

When we reach node_set_memory_tier_rank(), node1 (that has the pmem device)
is already part of memtier1 whose nodelist shows 0-1.

Regards,
Bharata.