linux-kernel - Re: [PATCH v6 00/14] Introduce Data Access MONitor (DAMON)

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Date:   Mon, 2 Mar 2020 12:35:12 +0100
From:   SeongJae Park <sjpark@...zon.com>
To:     <akpm@...ux-foundation.org>, SeongJae Park <sjpark@...zon.com>
CC:     SeongJae Park <sjpark@...zon.de>, <aarcange@...hat.com>,
        <yang.shi@...ux.alibaba.com>, <acme@...nel.org>,
        <alexander.shishkin@...ux.intel.com>, <amit@...nel.org>,
        <brendan.d.gregg@...il.com>, <brendanhiggins@...gle.com>,
        <cai@....pw>, <colin.king@...onical.com>, <corbet@....net>,
        <dwmw@...zon.com>, <jolsa@...hat.com>, <kirill@...temov.name>,
        <mark.rutland@....com>, <mgorman@...e.de>, <minchan@...nel.org>,
        <mingo@...hat.com>, <namhyung@...nel.org>, <peterz@...radead.org>,
        <rdunlap@...radead.org>, <rientjes@...gle.com>,
        <rostedt@...dmis.org>, <shuah@...nel.org>, <sj38.park@...il.com>,
        <vbabka@...e.cz>, <vdavydov.dev@...il.com>, <linux-mm@...ck.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 00/14] Introduce Data Access MONitor (DAMON)

Hello,

On Mon, 24 Feb 2020 13:30:33 +0100 SeongJae Park <sjpark@...zon.com> wrote:

> From: SeongJae Park <sjpark@...zon.de>
> 
> Introduction
> ============
> 
> Memory management decisions can be improved if finer data access information is
> available.  However, because such finer information usually comes with higher
> overhead, most systems including Linux forgives the potential improvement and
> rely on only coarse information or some light-weight heuristics.  The
> pseudo-LRU and the aggressive THP promotions are such examples.
> 
> A number of experimental data access pattern awared memory management
> optimizations (refer to 'Appendix A' for more details) say the sacrifices are
> huge.  However, none of those has successfully adopted to Linux kernel mainly
> due to the absence of a scalable and efficient data access monitoring
> mechanism.  Refer to 'Appendix B' to see the limitations of existing memory
> monitoring mechanisms.
> 
> DAMON is a data access monitoring subsystem for the problem.  It is 1) accurate
> enough to be used for the DRAM level memory management (a straightforward
> DAMON-based optimization achieved up to 2.55x speedup), 2) light-weight enough
> to be applied online (compared to a straightforward access monitoring scheme,
> DAMON is up to 94.242.42x lighter) and 3) keeps predefined upper-bound overhead
> regardless of the size of target workloads (thus scalable).  Refer to 'Appendix
> C' if you interested in how it is possible.
> 
> DAMON has mainly designed for the kernel's memory management mechanisms.
> However, because it is implemented as a standalone kernel module and provides
> several interfaces, it can be used by a wide range of users including kernel
> space programs, user space programs, programmers, and administrators.  DAMON
> is now supporting the monitoring only, but it will also provide simple and
> convenient data access pattern awared memory managements by itself.  Refer to
> 'Appendix D' for more detailed expected usages of DAMON.

I have posted this patchset once per week, but skip this week because there
were no comments in last week and therefore made no change in the patchset.

I think I answered to all previous comments and fixed all bugs previously
found.  May I ask some more comments or reviews?  If I missed something or
doing wrong, please let me know.


Thanks,
SeongJae Park

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