On Wed, 22 Dec 2021 19:14:39 +0800 Baolin Wang [off-list ref] 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.

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

And the DAMON user space tool?