From: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
To: Michal Hocko <mhocko@suse.com>
Cc: <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>,
<ying.huang@intel.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
Date: Tue, 5 Dec 2023 14:32:20 +0530 [thread overview]
Message-ID: <8eae7d95-fc98-4ac7-8f83-d0caee00bc87@micron.com> (raw)
In-Reply-To: <ZW7km-SED5oIGGnZ@tiehlicka>
On 12/5/2023 2:21 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 Tue 05-12-23 14:12:17, Srinivasulu Thanneeru wrote:
>>
>>
>> On 12/5/2023 2:05 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 Tue 05-12-23 01:26:07, Srinivasulu Thanneeru wrote:
>>>>
>>>>
>>>> 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.
>>>
>>> Presumably they are grouped based on a HW configuration. Does that mean
>>> that the configuration is wrong? Are you trying to workaround that by
>>> this interface?
>>>
>>>> 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.
>>>
>>> Again, could you expand a bit more and explain why this cannot be
>>> configured automatically?
>>
>> Yes, in both cases above, if hardware not automatically populated properly,
>> in that case this interface would help to correct it from user space.
>>
>> We had observed case-2 in our setups.
>
> How hard it is to address this at the HW level?
>
> Btw. this is really important piece of context that should be part of
> the changelog. Quite honestly introducing user interfaces solely to
> workaround HW issues seems a rather weak justification. Are there any
> usecases you can think of where this would be useful?
I'm not sure how difficult to fix it in the hardware.
Sure, i will capture the use-cases in the change log, will be sending V2
by changing interface from adistance_offset to memtier_overwrite to
avoid complicated math for finding offset at user-level.
Thank you Michal Hocko for the feedback.
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2023-12-05 9:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-30 22:04 [RFC PATCH 0/2] Node migration between memory tiers sthanneeru.opensrc
2023-11-30 22:04 ` [RFC PATCH 1/2] base/node: Add sysfs for adistance_offset sthanneeru.opensrc
2023-11-30 22:04 ` [RFC PATCH 2/2] memory tier: Support node migration between tiers sthanneeru.opensrc
2023-12-04 15:43 ` [RFC PATCH 0/2] Node migration between memory tiers Michal Hocko
2023-12-04 19:56 ` [EXT] " Srinivasulu Thanneeru
2023-12-05 8:35 ` Michal Hocko
2023-12-05 8:42 ` Srinivasulu Thanneeru
2023-12-05 8:51 ` Michal Hocko
2023-12-05 9:02 ` Srinivasulu Thanneeru [this message]
2023-12-05 9:09 ` Michal Hocko
2023-12-05 9:19 ` Ravi Jonnalagadda
2023-12-06 15:22 ` Michal Hocko
2023-12-05 8:51 ` [EXT] " Huang, Ying
2023-12-05 9:12 ` Huang, Ying
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