Re: [EXT] Re: [RFC PATCH v2 0/2] Node migration between memory tiers

[Huang, Ying]

Srinivasulu Thanneeru <sthanneeru@xxxxxxxxxx> writes:

> Micron Confidential
>
> Hi Huang, Ying,
>
> My apologies for wrong mail reply format, my mail client settings got changed on my PC.
> Please find comments bellow inline.
>
> Regards,
> Srini
>
>
> Micron Confidential
>> -----Original Message-----
>> From: Huang, Ying <ying.huang@xxxxxxxxx>
>> Sent: Monday, December 18, 2023 11:26 AM
>> To: gregory.price <gregory.price@xxxxxxxxxxxx>
>> Cc: Srinivasulu Opensrc <sthanneeru.opensrc@xxxxxxxxxx>; linux-
>> cxl@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; Srinivasulu Thanneeru
>> <sthanneeru@xxxxxxxxxx>; aneesh.kumar@xxxxxxxxxxxxx;
>> dan.j.williams@xxxxxxxxx; mhocko@xxxxxxxx; tj@xxxxxxxxxx;
>> john@xxxxxxxxxxxxxx; Eishan Mirakhur <emirakhur@xxxxxxxxxx>; Vinicius
>> Tavares Petrucci <vtavarespetr@xxxxxxxxxx>; Ravis OpenSrc
>> <Ravis.OpenSrc@xxxxxxxxxx>; Jonathan.Cameron@xxxxxxxxxx; linux-
>> kernel@xxxxxxxxxxxxxxx; Johannes Weiner <hannes@xxxxxxxxxxx>; Wei Xu
>> <weixugc@xxxxxxxxxx>
>> Subject: [EXT] Re: [RFC PATCH v2 0/2] Node migration between memory tiers
>>
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>>
>> Gregory Price <gregory.price@xxxxxxxxxxxx> writes:
>>
>> > On Fri, Dec 15, 2023 at 01:02:59PM +0800, Huang, Ying wrote:
>> >> <sthanneeru.opensrc@xxxxxxxxxx> writes:
>> >>
>> >> > =============
>> >> > Version Notes:
>> >> >
>> >> > V2 : Changed interface to memtier_override from adistance_offset.
>> >> > memtier_override was recommended by
>> >> > 1. John Groves <john@xxxxxxxxxxxxxx>
>> >> > 2. Ravi Shankar <ravis.opensrc@xxxxxxxxxx>
>> >> > 3. Brice Goglin <Brice.Goglin@xxxxxxxx>
>> >>
>> >> It appears that you ignored my comments for V1 as follows ...
>> >>
>> >>
>> https://lore.k/
>> ernel.org%2Flkml%2F87o7f62vur.fsf%40yhuang6-
>> desk2.ccr.corp.intel.com%2F&data=05%7C02%7Csthanneeru%40micron.com
>> %7C5e614e5f028342b6b59c08dbff8e3e37%7Cf38a5ecd28134862b11bac1d56
>> 3c806f%7C0%7C0%7C638384758666895965%7CUnknown%7CTWFpbGZsb3d
>> 8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3
>> D%7C3000%7C%7C%7C&sdata=OpMkYCar%2Fv8uHb7AvXbmaNltnXeTvcNUTi
>> bLhwV12Fg%3D&reserved=0
>
> Thank you, Huang, Ying for pointing to this.
> https://lpc.events/event/16/contributions/1209/attachments/1042/1995/Live%20In%20a%20World%20With%20Multiple%20Memory%20Types.pdf
>
> In the presentation above, the adistance_offsets are per memtype.
> We believe that adistance_offset per node is more suitable and flexible.
> since we can change it per node. If we keep adistance_offset per memtype,
> then we cannot change it for a specific node of a given memtype.
>
>> >>
>> https://lore.k/
>> ernel.org%2Flkml%2F87jzpt2ft5.fsf%40yhuang6-
>> desk2.ccr.corp.intel.com%2F&data=05%7C02%7Csthanneeru%40micron.com
>> %7C5e614e5f028342b6b59c08dbff8e3e37%7Cf38a5ecd28134862b11bac1d56
>> 3c806f%7C0%7C0%7C638384758666895965%7CUnknown%7CTWFpbGZsb3d
>> 8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3
>> D%7C3000%7C%7C%7C&sdata=O0%2B6T%2FgU0TicCEYBac%2FAyjOLwAeouh
>> D%2BcMI%2BflOsI1M%3D&reserved=0
>
> Yes, memory_type would be grouping the related memories together as single tier.
> We should also have a flexibility to move nodes between tiers, to address the issues.
> described in use cases above.

We don't pursue absolute flexibility.  We add necessary flexibility
only.  Why do you need this kind of flexibility?  Can you provide some
use cases where memory_type based "adistance_offset" doesn't work?

--
Best Regards,
Huang, Ying