Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) client-ip=23.128.96.38;
From:   "Huang, Ying" <ying.huang@intel.com>
To:     Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
Cc:     Michal Hocko <mhocko@suse.com>, <aneesh.kumar@linux.ibm.com>,
        <linux-cxl@vger.kernel.org>, <linux-mm@kvack.org>,
        <dan.j.williams@intel.com>, <hannes@cmpxchg.org>,
        <hasanalmaruf@fb.com>, <haowang3@fb.com>,
        <gregory.price@memverge.com>, <tj@kernel.org>,
        <hezhongkun.hzk@bytedance.com>, <fvdl@google.com>,
        <john@jagalactic.com>, <emirakhur@micron.com>,
        <vtavarespetr@micron.com>, <Ravis.OpenSrc@micron.com>,
        <Jonathan.Cameron@huawei.com>, <linux-kernel@vger.kernel.org>,
        <linux-api@vger.kernel.org>
Subject: Re: [EXT] Re: [RFC PATCH 0/2] Node migration between memory tiers
In-Reply-To: <1db561a9-6984-418d-9305-a2a5ece93696@micron.com> (Srinivasulu
        Thanneeru's message of "Tue, 5 Dec 2023 01:26:07 +0530")
References: <20231130220422.2033-1-sthanneeru.opensrc@micron.com>
        <ZW3zl2Fke5FtQCv3@tiehlicka>
        <1db561a9-6984-418d-9305-a2a5ece93696@micron.com>
Date:   Tue, 05 Dec 2023 16:51:02 +0800
Message-ID: <87jzpt2ft5.fsf@yhuang6-desk2.ccr.corp.intel.com>
User-Agent: Gnus/5.13 (Gnus v5.13)
MIME-Version: 1.0
Content-Type: text/plain; charset=ascii
Precedence: bulk

Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com> writes:

> On 12/4/2023 9:13 PM, Michal Hocko wrote:
>> CAUTION: EXTERNAL EMAIL. Do not click links or open attachments
>> unless you recognize the sender and were expecting this message.
>> On Fri 01-12-23 03:34:20, sthanneeru.opensrc@micron.com wrote:
>>> From: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
>>>
>>> The memory tiers feature allows nodes with similar memory types
>>> or performance characteristics to be grouped together in a
>>> memory tier. However, there is currently no provision for
>>> moving a node from one tier to another on demand.
>> Could you expand on why this is really needed/necessary? What is the
>> actual usecase?
>
> Hi Michal Hock,
>
> Following two use-cases we have observed.
> 1. It is not accurate to group similar memory types in the same tier,
>    because even similar memory types may have different speed grades.
>
> 2. Some systems boots up with CXL devices and DRAM on the same
> memory-tier, we need a way to move the CXL nodes to the correct tier
> from the user space.

I guess that you need to move all NUMA nodes with same performance
metrics together?  If so, That is why we previously proposed to place
the knob in "memory_type".

--
Best Regards,
Huang, Ying