linux-kernel - Re: [RFC] Memory Tiering

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Date:   Thu, 17 Oct 2019 07:17:05 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     David Hildenbrand <david@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>,
        Wu Fengguang <fengguang.wu@...el.com>,
        Huang Ying <ying.huang@...el.com>
Subject: Re: [RFC] Memory Tiering

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.