linux-kernel - Re: [RFC] Memory Tiering

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Message-ID: <34ae126d-002b-b773-96c9-a78f7ef671e9@redhat.com>
Date:   Thu, 17 Oct 2019 19:34:47 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Verma, Vishal L" <vishal.l.verma@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Wu, Fengguang" <fengguang.wu@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>
Subject: Re: [RFC] Memory Tiering

On 17.10.19 19:07, Verma, Vishal L wrote:
> 
> On Thu, 2019-10-17 at 07:17 -0700, Dave Hansen wrote:
>> On 10/17/19 1:07 AM, David Hildenbrand wrote:
>>> Very interesting topic. I heard similar demand from HPC folks
>>> (especially involving other memory types ("tiers")). There, I think
>>> you often want to let the application manage that. But of course, for
>>> many applications an automatic management might already be
>>> beneficial.
>>>
>>> Am I correct that you are using PMEM in this area along with
>>> ZONE_DEVICE and not by giving PMEM to the buddy (add_memory())?
>>
>> The PMEM starts out as ZONE_DEVICE, but we unbind it from its original
>> driver and bind it to this stub of a "driver": drivers/dax/kmem.c which
>> uses add_memory() on it.
>>
>> There's some nice tooling inside the daxctl component of ndctl to do all
>> the sysfs magic to make this happen.
>>
> Here is more info about the daxctl command in question:
> 
> https://pmem.io/ndctl/daxctl-reconfigure-device.html
> 

Thanks, yeah I saw the patches back then (I though they were by Pavel 
but they were actually by you :) ) to add the memory to the buddy (via 
add_memory()).

Will explore some more, thanks!

-- 

Thanks,

David / dhildenb