Re: [PATCH v3 updated] mm/demotion: Expose memory tier details via sysfs

Huang, Ying
2022-09-02T06:12:17Z

Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> writes:

> On 9/2/22 11:10 AM, Huang, Ying wrote:
>> Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> writes:
>>
>>> On 9/2/22 10:39 AM, Wei Xu wrote:
>>>> On Thu, Sep 1, 2022 at 5:33 PM Huang, Ying <ying.huang@intel.com> wrote:
>>>>>
>>>>> Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> writes:
>>>>>
>>>>>> On 9/1/22 12:31 PM, Huang, Ying wrote:
>>>>>>> "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
>>>>>>>
>>>>>>>> This patch adds /sys/devices/virtual/memory_tiering/ where all memory tier
>>>>>>>> related details can be found. All allocated memory tiers will be listed
>>>>>>>> there as /sys/devices/virtual/memory_tiering/memory_tierN/
>>>>>>>>
>>>>>>>> The nodes which are part of a specific memory tier can be listed via
>>>>>>>> /sys/devices/virtual/memory_tiering/memory_tierN/nodes
>>>>>>>
>>>>>>> I think "memory_tier" is a better subsystem/bus name than
>>>>>>> memory_tiering. Because we have a set of memory_tierN devices inside.
>>>>>>> "memory_tier" sounds more natural. I know this is subjective, just my
>>>>>>> preference.
>>>>>>>
>>>
>>>
>>> I missed replying to this earlier. I will keep memory_tiering as subsystem name in v4
>>> because we would want it to a susbsystem where all memory tiering related details can be found
>>> including memory type in the future. This is as per discussion
>>>
>>> https://lore.kernel.org/linux-mm/CAAPL-u9TKbHGztAF=r-io3gkX7gorUunS2UfstudCWuihrA=0g@mail.gmail.com
>>
>> I don't think that it's a good idea to mix 2 types of devices in one
>> subsystem (bus). If my understanding were correct, that breaks the
>> driver core convention.
>>
>
> All these are virtual devices .I am not sure i follow what you mean by 2 types of devices.
> memory_tiering is a subsystem that represents all the details w.r.t memory tiering. It shows
> details of memory tiers and can possibly contain details of different memory types .

IMHO, memory_tier and memory_type are 2 kind of devices. They have
almost totally different attributes (sysfs file). So, we should create
2 buses for them. Each has its own attribute group. "virtual" itself
isn't a subsystem.

Best Regards,
Huang, Ying