linux-kernel - Re: [PATCH v22 03/18] mm/damon: Adaptively adjust regions

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Message-ID: <20201126121226.18883-1-sjpark@amazon.com>
Date:   Thu, 26 Nov 2020 13:12:26 +0100
From:   SeongJae Park <sjpark@...zon.com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     SeongJae Park <sjpark@...zon.com>,
        SeongJae Park <sjpark@...zon.de>,
        <Jonathan.Cameron@...wei.com>,
        Andrea Arcangeli <aarcange@...hat.com>, <acme@...nel.org>,
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Subject: Re: [PATCH v22 03/18] mm/damon: Adaptively adjust regions

On Wed, 25 Nov 2020 07:29:41 -0800 Shakeel Butt <shakeelb@...gle.com> wrote:

> On Tue, Oct 20, 2020 at 2:01 AM SeongJae Park <sjpark@...zon.com> wrote:
> >
> > From: SeongJae Park <sjpark@...zon.de>
> >
> > Even somehow the initial monitoring target regions are well constructed
> > to fulfill the assumption (pages in same region have similar access
> > frequencies), the data access pattern can be dynamically changed.  This
> > will result in low monitoring quality.  To keep the assumption as much
> > as possible, DAMON adaptively merges and splits each region based on
> > their access frequency.
> >
> > For each ``aggregation interval``, it compares the access frequencies of
> > adjacent regions and merges those if the frequency difference is small.
> > Then, after it reports and clears the aggregated access frequency of
> > each region, it splits each region into two or three regions if the
> > total number of regions will not exceed the user-specified maximum
> > number of regions after the split.
> >
> > In this way, DAMON provides its best-effort quality and minimal overhead
> > while keeping the upper-bound overhead that users set.
> >
> > Signed-off-by: SeongJae Park <sjpark@...zon.de>
> > Reviewed-by: Leonard Foerster <foersleo@...zon.de>
> 
> The high level comment I have is that kdamond_[merge|split]_regions
> should be part of the abstraction of the target instead of the damon
> context.

Agreed in a high level.  Please refer to my answer to your second suggestion at
https://lore.kernel.org/linux-mm/20201126115157.6888-1-sjpark@amazon.com/


Thanks,
SeongJae Park