linux-kernel - Re: [PATCH v20 00/15] Introduce Data Access MONitor (DAMON)

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Date:   Fri, 25 Sep 2020 16:59:19 +0200
From:   SeongJae Park <sjpark@...zon.com>
To:     SeongJae Park <sjpark@...zon.com>
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Subject: Re: [PATCH v20 00/15] Introduce Data Access MONitor (DAMON)

On Mon, 31 Aug 2020 13:22:35 +0200 SeongJae Park <sjpark@...zon.com> wrote:

> On Thu, 20 Aug 2020 09:27:38 +0200 SeongJae Park <sjpark@...zon.com> wrote:
> 
> > On Mon, 17 Aug 2020 12:51:22 +0200 SeongJae Park <sjpark@...zon.com> wrote:
> > 
> > > From: SeongJae Park <sjpark@...zon.de>
> > > 
[...]
> > > Introduction
> > > ============
> > > 
> > > DAMON is a data access monitoring framework subsystem for the Linux kernel.
> > > The core mechanisms of DAMON called 'region based sampling' and 'adaptive
> > > regions adjustment' (refer to 'mechanisms.rst' in the 11th patch of this
> > > patchset for the detail) make it
> > > 
> > >  - accurate (The monitored information is useful for DRAM level memory
> > >    management. It might not appropriate for Cache-level accuracy, though.),
> > >  - light-weight (The monitoring overhead is low enough to be applied online
> > >    while making no impact on the performance of the target workloads.), and
> > >  - scalable (the upper-bound of the instrumentation overhead is controllable
> > >    regardless of the size of target workloads.).
> > > 
> > > Using this framework, therefore, the kernel's core memory management mechanisms
> > > such as reclamation and THP can be optimized for better memory management.  The
> > > experimental memory management optimization works that incurring high
> > > instrumentation overhead will be able to have another try.  In user space,
> > > meanwhile, users who have some special workloads will be able to write
> > > personalized tools or applications for deeper understanding and specialized
> > > optimizations of their systems.
> > 
> > DAMON will be presented in the next week LPC[1].  To be prepared for a screen
> > sharing error (if I get no such error, I will do a live-demo), I recorded a
> > simple demo video.  I would like to share it here to help your easier
> > understanding of DAMON.
> > 
> >     https://youtu.be/l63eqbVBZRY
> > 
> > [1] https://linuxplumbersconf.org/event/7/contributions/659/
> 
> During the session, I introduced the list of future works and asked the
> audiences to vote for the priority of the tasks:
> https://youtu.be/jOBkKMA0uF0?t=13253

I also promised to make my automated tests for DAMON available as open source.
I'm happy to announce that it is not available at Github[1] under GPL v2
license.  Using that, you can easily test how well DAMON works on your machine.
Hopefully, it could be used as a getting started guide for both users and
developers of DAMON.

[1] https://github.com/awslabs/damon-tests


Thanks,
SeongJae Park

> 
> To summarize here, the tasks are (highest priority first):
> 
> 1. Make current DAMON patchset series merged in the mainline (6 votes)
> 2. User space interface improvement (4 votes)
>  - Multiple monitoring contexts
>  - Charging of the monitoring threads' CPU usage
> 3. Support more address spaces (2 votes)
>  - Cgroups, cached pages, specific file-backed pages, swap slots, ...
> 3. DAMON-based MM optimizations (2 votes)
>  - Page reclaim, THP, compaction, NUMA balancing, ...
> 4. Optimize for special use-cases (1 vote)
>  - Page granularity monitoring, accessed-or-not monitoring, ...
> 
> So, I'd like to focus on polishing current patchset so that it could be merged
> in.  For that, I'd like to ask your more reviews.
> 
> While waiting for the reviews, I will start implementing other future features
> that received many votes.  The support of multiple monitoring contexts for the
> user space would be the first one.  Once the implementation is finished, I will
> post it as separated RFC patchset (the user space interface will be compatible
> with current one).
> 
> Any comment is welcome.
> 
> 
> Thanks,
> SeongJae Park