Re: [PATCH v2 0/2] Add a new scheme to support demotion on tiered memory system

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 12/23/2021 8:01 AM, Andrew Morton wrote:
> On Wed, 22 Dec 2021 19:14:39 +0800 Baolin Wang <baolin.wang@linux.alibaba.com> wrote:
> 
>> Now on tiered memory system with different memory types, the reclaim path in
>> shrink_page_list() already support demoting pages to slow memory node instead
>> of discarding the pages. However, at that time the fast memory node memory
>> wartermark is already tense, which will increase the memory allocation latency
>> during page demotion. So a new method from user space demoting cold pages
>> proactively will be more helpful.
>>
>> We can rely on the DAMON in user space to help to monitor the cold memory on
>> fast memory node, and demote the cold pages to slow memory node proactively to
>> keep the fast memory node in a healthy state.
>>
>> This patch set introduces a new scheme named DAMOS_DEMOTE to support this feature,
>> and works well from my testing. Any comments are welcome. Thanks.
> 
> This is interesting.
> 
> I think it would be helpful if we could have some example scenarios in
> this changelog, help people understand how to use DAMOS_DEMOTE and what
> effects it has.

Sure.

> 
> Documentation/admin-guide/mm/damon/usage.rst would like an update?

Ah, I missed updating de Doc, and will do in v3.

> And the DAMON user space tool?

Yes. Thanks for your comments.