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

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Message-Id: <20211221132617.15064-1-sj@kernel.org>
Date:   Tue, 21 Dec 2021 13:26:17 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     sj@...nel.org, akpm@...ux-foundation.org, ying.huang@...el.com,
        dave.hansen@...ux.intel.com, ziy@...dia.com, shy828301@...il.com,
        zhongjiang-ali@...ux.alibaba.com, xlpang@...ux.alibaba.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Add a new scheme to support demotion on tiered memory system

Hi Baolin,

On Tue, 21 Dec 2021 17:18:02 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:

> Hi,
> 
> 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.

I like the idea, thank you for these patches!  If possible, could you share
some details about your tests?


Thanks,
SJ

> 
> 
> Baolin Wang (2):
>   mm: Export the alloc_demote_page() function
>   mm/damon: Add a new scheme to support demotion on tiered memory system
> 
>  include/linux/damon.h |   3 +
>  mm/damon/dbgfs.c      |   1 +
>  mm/damon/vaddr.c      | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  mm/internal.h         |   1 +
>  mm/vmscan.c           |   2 +-
>  5 files changed, 162 insertions(+), 1 deletion(-)
> 
> -- 
> 1.8.3.1