linux-kernel - Re: [PATCH v22 00/18] Introduce Data Access MONitor (DAMON)

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Date:   Tue, 17 Nov 2020 09:05:39 +0100
From:   SeongJae Park <sjpark@...zon.com>
To:     SeongJae Park <sjpark@...zon.com>
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Subject: Re: [PATCH v22 00/18] Introduce Data Access MONitor (DAMON)

Another week, another ping.  I'm waiting for _any_ comments.


Thanks,
SeongJae Park

On Wed, 11 Nov 2020 17:41:13 +0100 SeongJae Park <sjpark@...zon.com> wrote:

> Hi, I'd like to remind you that I'm still waiting more reviews.  Any comments
> are welcome.
> 
> 
> Thanks,
> SeongJae Park
> 
> On Tue, 20 Oct 2020 10:59:22 +0200 SeongJae Park <sjpark@...zon.com> wrote:
> 
> > From: SeongJae Park <sjpark@...zon.de>
> > 
> > Changes from Previous Version (v21)
> > ===================================
> > 
> > This version contains below minor changes.
> > 
> > - Fix build warnings and errors (kernel test robot)
> > - Fix a memory leak (kmemleak)
> > - Respect KUNIT_ALL_TESTS
> > - Rebase on v5.9
> > - Update the evaluation results
> > 
> > Introduction
> > ============
> > 
> > DAMON is a data access monitoring framework 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, several memory management mechanisms such as
> > reclamation and THP can be optimized to aware real data access patterns.
> > Experimental access pattern aware memory management optimization works that
> > incurring high instrumentation overhead will be able to have another try.
> > 
> > Though DAMON is for kernel subsystems, it can be easily exposed to the user
> > space by writing a DAMON-wrapper kernel subsystem.  Then, user space users who
> > have some special workloads will be able to write personalized tools or
> > applications for deeper understanding and specialized optimizations of their
> > systems.
> > 
> > Evaluations
> > ===========
> > 
> > We evaluated DAMON's overhead, monitoring quality and usefulness using 24
> > realistic workloads on my QEMU/KVM based virtual machine running a kernel that
> > v22 DAMON patchset is applied.
> > 
> > DAMON is lightweight.  It increases system memory usage by 0.25% and slows
> > target workloads down by 0.89%.
> > 
> > DAMON is accurate and useful for memory management optimizations.  An
> > experimental DAMON-based operation scheme for THP, 'ethp', removes 81.73% of
> > THP memory overheads while preserving 95.29% of THP speedup.  Another
> > experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
> > reduces 91.30% of residential sets and 23.45% of system memory footprint while
> > incurring only 2.08% runtime overhead in the best case (parsec3/freqmine).
> > 
> > NOTE that the experimentail THP optimization and proactive reclamation are not
> > for production but only for proof of concepts.
> > 
> > Please refer to the official document[1] or "Documentation/admin-guide/mm: Add
> > a document for DAMON" patch in this patchset for detailed evaluation setup and
> > results.
> > 
> > [1] https://damonitor.github.io/doc/html/latest-damon/admin-guide/mm/damon/eval.html
> >