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    Subject[PATCH v13 00/15] Introduce Data Access MONitor (DAMON)
    Date
    From: SeongJae Park <sjpark@amazon.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 :doc:`mechanisms` for the detail) make it
    accurate, efficient, and scalable. Using this framework, therefore, the
    kernel's core memory management mechanisms including reclamation and THP can be
    optimized for better memory management. The memory management optimization
    works that have not merged into the mainline due to their high data access
    monitoring 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 more understanding and specialized
    optimizations of their systems using the DAMON as a framework.

    Evaluations
    ===========

    We evaluated DAMON's overhead, monitoring quality and usefulness using 25
    realistic workloads on my QEMU/KVM based virtual machine.

    DAMON is lightweight. It increases system memory usage by only -0.39% and
    consumes less than 1% CPU time in most case. It slows target workloads down by
    only 0.63%.

    DAMON is accurate and useful for memory management optimizations. An
    experimental DAMON-based operation scheme for THP, 'ethp', removes 69.43% of
    THP memory overheads while preserving 37.11% of THP speedup. Another
    experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
    reduces 89.30% of residential sets and 22.40% of system memory footprint while
    incurring only 1.98% runtime overhead in the best case (parsec3/freqmine).

    NOTE that the experimentail THP optimization and proactive reclamation are not
    for production, just 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

    More Information
    ================

    We prepared a showcase web site[1] that you can get more information. There
    are

    - the official documentations[2],
    - the heatmap format dynamic access pattern of various realistic workloads for
    heap area[3], mmap()-ed area[4], and stack[5] area,
    - the dynamic working set size distribution[6] and chronological working set
    size changes[7], and
    - the latest performance test results[8].

    [1] https://damonitor.github.io
    [2] https://damonitor.github.io/doc/html/latest-damon
    [3] https://damonitor.github.io/test/result/visual/latest/heatmap.0.html
    [4] https://damonitor.github.io/test/result/visual/latest/heatmap.1.html
    [5] https://damonitor.github.io/test/result/visual/latest/heatmap.2.html
    [6] https://damonitor.github.io/test/result/visual/latest/wss_sz.html
    [7] https://damonitor.github.io/test/result/visual/latest/wss_time.html
    [8] https://damonitor.github.io/test/result/perf/latest/html/index.html

    Baseline and Complete Git Trees
    ===============================

    The patches are based on the v5.6. You can also clone the complete git
    tree:

    $ git clone git://github.com/sjp38/linux -b damon/patches/v13

    The web is also available:
    https://github.com/sjp38/linux/releases/tag/damon/patches/v13

    There are a couple of trees for entire DAMON patchset series. It includes
    future features. The first one[1] contains the changes for latest release,
    while the other one[2] contains the changes for next release.

    [1] https://github.com/sjp38/linux/tree/damon/master
    [2] https://github.com/sjp38/linux/tree/damon/next

    Sequence Of Patches
    ===================

    The patches are organized in the following sequence. The first two patches are
    preparation of DAMON patchset. The 1st patch adds typos found in previous
    versions of DAMON patchset to 'scripts/spelling.txt' so that the typos can be
    caught by 'checkpatch.pl'. The 2nd patch exports 'lookup_page_ext()' to GPL
    modules so that it can be used by DAMON even though it is built as a loadable
    module.

    Next five patches implement the core of DAMON and it's programming interface.
    The 3rd patch introduces DAMON module, it's data structures, and data structure
    related common functions. Following four patches (4nd to 7th) implements the
    core mechanisms of DAMON, namely regions based sampling (patch 4), adaptive
    regions adjustment (patches 5-6), and dynamic memory mapping chage adoption
    (patch 7).

    Following four patches are for low level users of DAMON. The 8th patch
    implements callbacks for each of monitoring steps so that users can do whatever
    they want with the access patterns. The 9th one implements recording of access
    patterns in DAMON for better convenience and efficiency. Each of next two
    patches (10th and 11th) respectively adds a debugfs interface for privileged
    people and/or programs in user space, and a tracepoint for other tracepoints
    supporting tracers such as perf.

    Two patches for high level users of DAMON follows. To provide a minimal
    reference to the debugfs interface and for high level use/tests of the DAMON,
    the next patch (12th) implements an user space tool. The 13th patch adds a
    document for administrators of DAMON.

    Next two patches are for tests. The 14th and 15th patches provide unit tests
    (based on kunit) and user space tests (based on kselftest), respectively.

    Finally, the last patch (16th) updates the MAINTAINERS file.

    Patch History
    =============

    Changes from v12
    (https://lore.kernel.org/linux-mm/20200518100018.2293-1-sjpark@amazon.com/)
    - Avoid races between debugfs readers and writers
    - Add kernel-doc comments in damon.h

    Changes from v11
    (https://lore.kernel.org/linux-mm/20200511123302.12520-1-sjpark@amazon.com/)
    - Rewrite the document (Stefan Nuernberger)
    - Make 'damon_for_each_*' argument order consistent (Leonard Foerster)
    - Fix wrong comment in 'kdamond_merge_regions()' (Leonard Foerster)

    Changes from v10
    (https://lore.kernel.org/linux-mm/20200505110815.10532-1-sjpark@amazon.com/)
    - Reduce aggressive split overhead by doing it only if required

    Changes from v9
    (https://lore.kernel.org/linux-mm/20200427120442.24179-1-sjpark@amazon.com/)
    - Split each region into 4 subregions if possible (Jonathan Cameraon)
    - Update kunit test for the split code change

    Changes from v8
    (https://lore.kernel.org/linux-mm/20200406130938.14066-1-sjpark@amazon.com/)
    - Make regions always aligned by minimal region size that can be changed
    (Stefan Nuernberger)
    - Store binary format version in the recording file (Stefan Nuernberger)
    - Use 'int' for pid instead of 'unsigned long' (Stefan Nuernberger)
    - Fix a race condition in damon thread termination (Stefan Nuernberger)
    - Optimize random value generation and recording (Stefan Nuernberger)
    - Clean up commit messages and comments (Stefan Nuernberger)
    - Clean up code (Stefan Nuernberger)
    - Use explicit signalling and 'do_exit()' for damon thread termination
    - Add more typos to spelling.txt
    - Update the performance evaluation results
    - Describe future plans in the cover letter

    Changes from v7
    (https://lore.kernel.org/linux-mm/20200318112722.30143-1-sjpark@amazon.com/)
    - Cleanup variable names (Jonathan Cameron)
    - Split sampling address setup from access_check() (Jonathan Cameron)
    - Make sampling address to always locate in the region (Jonathan Cameron)
    - Make initial region's sampling addr to be old (Jonathan Cameron)
    - Split kdamond on/off function to seperate functions (Jonathan Cameron)
    - Fix wrong kernel doc comments (Jonathan Cameron)
    - Reset 'last_accessed' to false in kdamond_check_access() if necessary
    - Rebase on v5.6

    Please refer to v7 patchset to get older history.

    SeongJae Park (15):
    scripts/spelling: Add a few more typos
    mm/page_ext: Export lookup_page_ext() to GPL modules
    mm: Introduce Data Access MONitor (DAMON)
    mm/damon: Implement region based sampling
    mm/damon: Adaptively adjust regions
    mm/damon: Apply dynamic memory mapping changes
    mm/damon: Implement callbacks
    mm/damon: Implement access pattern recording
    mm/damon: Add debugfs interface
    mm/damon: Add tracepoints
    tools: Add a minimal user-space tool for DAMON
    Documentation/admin-guide/mm: Add a document for DAMON
    mm/damon: Add kunit tests
    mm/damon: Add user space selftests
    MAINTAINERS: Update for DAMON

    Documentation/admin-guide/mm/damon/api.rst | 20 +
    .../admin-guide/mm/damon/damon_heatmap.png | Bin 0 -> 8366 bytes
    .../admin-guide/mm/damon/damon_wss_change.png | Bin 0 -> 7211 bytes
    .../admin-guide/mm/damon/damon_wss_dist.png | Bin 0 -> 6173 bytes
    Documentation/admin-guide/mm/damon/eval.rst | 215 +++
    Documentation/admin-guide/mm/damon/faq.rst | 39 +
    .../admin-guide/mm/damon/freqmine_heatmap.png | Bin 0 -> 8687 bytes
    .../admin-guide/mm/damon/freqmine_wss_sz.png | Bin 0 -> 4986 bytes
    .../mm/damon/freqmine_wss_time.png | Bin 0 -> 6283 bytes
    Documentation/admin-guide/mm/damon/guide.rst | 196 +++
    Documentation/admin-guide/mm/damon/index.rst | 51 +
    .../admin-guide/mm/damon/mechanisms.rst | 111 ++
    Documentation/admin-guide/mm/damon/plans.rst | 49 +
    Documentation/admin-guide/mm/damon/start.rst | 119 ++
    .../mm/damon/streamcluster_heatmap.png | Bin 0 -> 37916 bytes
    .../mm/damon/streamcluster_wss_sz.png | Bin 0 -> 5522 bytes
    .../mm/damon/streamcluster_wss_time.png | Bin 0 -> 6322 bytes
    Documentation/admin-guide/mm/damon/usage.rst | 305 ++++
    Documentation/admin-guide/mm/index.rst | 1 +
    Documentation/index.rst | 176 +-
    MAINTAINERS | 12 +
    include/linux/damon.h | 136 ++
    include/trace/events/damon.h | 43 +
    mm/Kconfig | 23 +
    mm/Makefile | 1 +
    mm/damon-test.h | 622 +++++++
    mm/damon.c | 1517 +++++++++++++++++
    mm/page_ext.c | 1 +
    scripts/spelling.txt | 8 +
    tools/damon/.gitignore | 1 +
    tools/damon/_dist.py | 36 +
    tools/damon/_recfile.py | 23 +
    tools/damon/bin2txt.py | 67 +
    tools/damon/damo | 37 +
    tools/damon/heats.py | 362 ++++
    tools/damon/nr_regions.py | 91 +
    tools/damon/record.py | 212 +++
    tools/damon/report.py | 45 +
    tools/damon/wss.py | 97 ++
    tools/testing/selftests/damon/Makefile | 7 +
    .../selftests/damon/_chk_dependency.sh | 28 +
    tools/testing/selftests/damon/_chk_record.py | 108 ++
    .../testing/selftests/damon/debugfs_attrs.sh | 139 ++
    .../testing/selftests/damon/debugfs_record.sh | 50 +
    44 files changed, 4780 insertions(+), 168 deletions(-)
    create mode 100644 Documentation/admin-guide/mm/damon/api.rst
    create mode 100644 Documentation/admin-guide/mm/damon/damon_heatmap.png
    create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_change.png
    create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_dist.png
    create mode 100644 Documentation/admin-guide/mm/damon/eval.rst
    create mode 100644 Documentation/admin-guide/mm/damon/faq.rst
    create mode 100644 Documentation/admin-guide/mm/damon/freqmine_heatmap.png
    create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_sz.png
    create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_time.png
    create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
    create mode 100644 Documentation/admin-guide/mm/damon/index.rst
    create mode 100644 Documentation/admin-guide/mm/damon/mechanisms.rst
    create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
    create mode 100644 Documentation/admin-guide/mm/damon/start.rst
    create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_heatmap.png
    create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png
    create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_time.png
    create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
    create mode 100644 include/linux/damon.h
    create mode 100644 include/trace/events/damon.h
    create mode 100644 mm/damon-test.h
    create mode 100644 mm/damon.c
    create mode 100644 tools/damon/.gitignore
    create mode 100644 tools/damon/_dist.py
    create mode 100644 tools/damon/_recfile.py
    create mode 100644 tools/damon/bin2txt.py
    create mode 100755 tools/damon/damo
    create mode 100644 tools/damon/heats.py
    create mode 100644 tools/damon/nr_regions.py
    create mode 100644 tools/damon/record.py
    create mode 100644 tools/damon/report.py
    create mode 100644 tools/damon/wss.py
    create mode 100644 tools/testing/selftests/damon/Makefile
    create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
    create mode 100644 tools/testing/selftests/damon/_chk_record.py
    create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
    create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

    --
    2.17.1

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