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Message-ID: <a3a7a8fe-5b54-d4ea-fdbf-c4b719c684d3@linux.ibm.com>
Date:   Mon, 6 Jun 2022 18:30:51 +0530
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Subject: Re: [RFC PATCH v4 4/7] mm/demotion/dax/kmem: Set node's memory tier
 to MEMORY_TIER_PMEM
Content-Language: en-US
To:     Bharata B Rao <bharata@amd.com>, linux-mm@kvack.org,
        akpm@linux-foundation.org
Cc:     Huang Ying <ying.huang@intel.com>,
        Greg Thelen <gthelen@google.com>,
        Yang Shi <shy828301@gmail.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Tim C Chen <tim.c.chen@intel.com>,
        Brice Goglin <brice.goglin@gmail.com>,
        Michal Hocko <mhocko@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Hesham Almatary <hesham.almatary@huawei.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Alistair Popple <apopple@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Feng Tang <feng.tang@intel.com>,
        Jagdish Gediya <jvgediya@linux.ibm.com>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        David Rientjes <rientjes@google.com>
References: <CAAPL-u-dFp7PwPH6DfbYdnY8xaGsHz3tRQ0CPGVkiqURvdN8=A@mail.gmail.com>
 <20220527122528.129445-1-aneesh.kumar@linux.ibm.com>
 <20220527122528.129445-5-aneesh.kumar@linux.ibm.com>
 <5706f5e9-0609-98c9-a0cd-7d96336d73dd@amd.com>
 <8e651a1e-d189-3e8a-438f-298f21402bd2@linux.ibm.com>
 <d45374fa-6e51-36cb-9a2c-96f85d9de528@amd.com>
 <c98eb873-a5bb-edcc-743d-89cfffe52cd9@linux.ibm.com>
 <d6c94fd5-053b-7e6f-dc4e-83184ecf131a@amd.com>
 <a844c8c9-e1e1-2ccb-d58c-a5a608afabc0@linux.ibm.com>
 <87fski80sx.fsf@linux.ibm.com> <eaf22a62-73c7-d96b-fcd8-4437eb3d8559@amd.com>
From:   Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
In-Reply-To: <eaf22a62-73c7-d96b-fcd8-4437eb3d8559@amd.com>
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On 6/6/22 5:39 PM, Bharata B Rao wrote:
> On 6/6/2022 5:24 PM, Aneesh Kumar K.V wrote:
>> Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> writes:
>>>
>> Can you try this change?
>>
>> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
>> index 7a11c387fbbc..905609260dda 100644
>> --- a/drivers/dax/kmem.c
>> +++ b/drivers/dax/kmem.c
>> @@ -94,6 +94,17 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
>>   		goto err_reg_mgid;
>>   	data->mgid = rc;
>>   
>> +	/*
>> +	 * This get called before the node is brought online. That
>> +	 * is because depending on the value of mhp_default_online_type
>> +	 * the kernel will online the memory along with hotplug
>> +	 * operation. Add the new memory tier before we try to bring
>> +	 * memory blocks online. Otherwise new node will get added to
>> +	 * the default memory tier via hotplug callbacks.
>> +	 */
>> +#ifdef CONFIG_TIERED_MEMORY
>> +	node_set_memory_tier(numa_node, MEMORY_TIER_PMEM);
>> +#endif
>>   	for (i = 0; i < dev_dax->nr_range; i++) {
>>   		struct resource *res;
>>   		struct range range;
>> @@ -148,9 +159,6 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
>>   
>>   	dev_set_drvdata(dev, data);
>>   
>> -#ifdef CONFIG_TIERED_MEMORY
>> -	node_set_memory_tier(numa_node, MEMORY_TIER_PMEM);
>> -#endif
>>   	return 0;
>>   
>>   err_request_mem:
> 
> Yes, this fixes the issue for me. Thanks.
> 

I might put the below change instead of the above. In the end I guess it 
is better to add a NUMA node to memory tier after the node is brought 
online than before even though with the current code it shouldn't matter 
much.

modified   drivers/dax/kmem.c
@@ -147,9 +147,15 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
  	}

  	dev_set_drvdata(dev, data);
-
+	/*
+	 * node_reset_memory_tier is used here to ensure we force
+	 * update the NUMA node memory tier. Depending on the value
+	 * of mhp_default_online_type the kernel will online the memory
+	 * blocks along with hotplug operation above. This can result in dax
+	 * kmem memory NUMA node getting added to default memory tier.
+	 */
  #ifdef CONFIG_TIERED_MEMORY
-	node_set_memory_tier(numa_node, MEMORY_TIER_PMEM);
+	node_reset_memory_tier(numa_node, MEMORY_TIER_PMEM);
  #endif
  	return 0;