linux-kernel - Re: [PATCH v6 04/13] mm/demotion/dax/kmem: Set node's memory tier to MEMORY_TIER

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Message-ID: <81e5904b-73f7-2977-d135-2d27c6c216ac@linux.ibm.com>
Date:   Mon, 13 Jun 2022 12:35:27 +0530
From:   Aneesh Kumar K V <aneesh.kumar@...ux.ibm.com>
To:     Ying Huang <ying.huang@...el.com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org
Cc:     Wei Xu <weixugc@...gle.com>, Greg Thelen <gthelen@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Tim C Chen <tim.c.chen@...el.com>,
        Brice Goglin <brice.goglin@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Hesham Almatary <hesham.almatary@...wei.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Alistair Popple <apopple@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Feng Tang <feng.tang@...el.com>,
        Jagdish Gediya <jvgediya@...ux.ibm.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v6 04/13] mm/demotion/dax/kmem: Set node's memory tier to
 MEMORY_TIER_PMEM

On 6/13/22 12:29 PM, Ying Huang wrote:
> On Fri, 2022-06-10 at 19:22 +0530, Aneesh Kumar K.V wrote:
>> By default, all nodes are assigned to DEFAULT_MEMORY_TIER which
>> is the memory tier designated for nodes with DRAM
>>
>> Set dax kmem device node's tier to MEMORY_TIER_PMEM. MEMORY_TIER_PMEM
>> is assigned a default rank value of 100 and appears below DEFAULT_MEMORY_TIER
>> in demotion order.
>>
>> Signed-off-by: Jagdish Gediya <jvgediya@...ux.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
>> ---
>>   drivers/dax/kmem.c           |  4 ++
>>   include/linux/memory-tiers.h |  1 +
>>   mm/memory-tiers.c            | 78 ++++++++++++++++++++++++++++++++++++
>>   3 files changed, 83 insertions(+)
>>
>> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
>> index a37622060fff..0cb3de3d138f 100644
>> --- a/drivers/dax/kmem.c
>> +++ b/drivers/dax/kmem.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/fs.h>
>>   #include <linux/mm.h>
>>   #include <linux/mman.h>
>> +#include <linux/memory-tiers.h>
>>   #include "dax-private.h"
>>   #include "bus.h"
>>   
>>
>> @@ -147,6 +148,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
>>   
>>
>>   	dev_set_drvdata(dev, data);
>>   
>>
>> +#ifdef CONFIG_TIERED_MEMORY
>> +	node_create_and_set_memory_tier(numa_node, MEMORY_TIER_PMEM);
>> +#endif
>>   	return 0;
>>   
>>
>>   err_request_mem:
>> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
>> index 44c3c3b16a36..e102ec73ab80 100644
>> --- a/include/linux/memory-tiers.h
>> +++ b/include/linux/memory-tiers.h
>> @@ -18,6 +18,7 @@
>>   #define MAX_MEMORY_TIERS  3
>>   
>>
>>   extern bool numa_demotion_enabled;
>> +int node_create_and_set_memory_tier(int node, int tier);
>>   #else
>>   #define numa_demotion_enabled	false
>>   
>>
>> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
>> index c3123a457d90..00d393a5a628 100644
>> --- a/mm/memory-tiers.c
>> +++ b/mm/memory-tiers.c
>> @@ -67,6 +67,84 @@ static struct memory_tier *register_memory_tier(unsigned int tier,
>>   	return memtier;
>>   }
>>   
>>
>> +static struct memory_tier *__node_get_memory_tier(int node)
>> +{
>> +	struct memory_tier *memtier;
>> +
>> +	list_for_each_entry(memtier, &memory_tiers, list) {
>> +		if (node_isset(node, memtier->nodelist))
>> +			return memtier;
>> +	}
>> +	return NULL;
>> +}
>> +
> 
> I suggest to add NODE_DATA(nid)->mem_tier before this patch.  That is,
> part of [9/13].  That will make code much simpler and easier to
> review.
> 

I would still like to keep introducing that NODE_DATA()->memtier later, 
so that the everything before that can be reviewed with simpler locking. 
__node_get_memory_tier() get fixed in patch 9 where all the details of 
that lockless access is documented. This also enables one to look at the 
history later.

> And, in addition to dax_kmem, whenever a normal node is onlined, we
> need to add it to the default memory tier.  I found this is done in
> [5/13].  IMHO, we should move that part before this patch.
>

Sure will move the hotplug callback earlier.


-aneesh