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Date:   Fri, 27 May 2022 19:10:55 +0530
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Subject: Re: RFC: Memory Tiering Kernel Interfaces (v3)
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To:     Wei Xu <weixugc@google.com>, Huang Ying <ying.huang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Thelen <gthelen@google.com>,
        Yang Shi <shy828301@gmail.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Tim C Chen <tim.c.chen@intel.com>,
        Brice Goglin <brice.goglin@gmail.com>,
        Michal Hocko <mhocko@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Hesham Almatary <hesham.almatary@huawei.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Alistair Popple <apopple@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Feng Tang <feng.tang@intel.com>, Linux MM <linux-mm@kvack.org>,
        Jagdish Gediya <jvgediya@linux.ibm.com>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        David Rientjes <rientjes@google.com>
References: <CAAPL-u-dFp7PwPH6DfbYdnY8xaGsHz3tRQ0CPGVkiqURvdN8=A@mail.gmail.com>
From:   Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
In-Reply-To: <CAAPL-u-dFp7PwPH6DfbYdnY8xaGsHz3tRQ0CPGVkiqURvdN8=A@mail.gmail.com>
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On 5/27/22 2:52 AM, Wei Xu wrote:

>    The order of memory tiers is determined by their rank values, not by
>    their memtier device names.
> 
>    - /sys/devices/system/memtier/possible
> 
>      Format: ordered list of "memtier(rank)"
>      Example: 0(64), 1(128), 2(192)
> 
>      Read-only.  When read, list all available memory tiers and their
>      associated ranks, ordered by the rank values (from the highest
>       tier to the lowest tier).
> 

Did we discuss the need for this? I haven't done this in the patch 
series I sent across. We do have 
/sys/devices/system/memtier/default_rank which should allow user to 
identify the default rank to which memory would get added via hotplug if 
the NUMA node is not part of any memory tier.


-aneesh