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    Subject[PATCH 0/2] Adding two writeback files in /proc/sys/vm
    Patch #1 sets up some helper functions for accounting.

    Patch #2 adds writeback files for visibility

    To help developers and applications gain visibility into writeback
    behaviour adding two read-only sysctl files into /proc/sys/vm.
    These files allow user apps to understand writeback behaviour over time
    and learn how it is impacting their performance.

    # cat /proc/sys/vm/pages_dirtied
    # cat /proc/sys/vm/pages_entered_writeback

    These two new files are necessary to give visibility into writeback
    behaviour. We have /proc/diskstats which lets us understand the io in
    the block layer. We have blktrace for more in depth understanding. We have
    e2fsprogs and debugsfs to give insight into the file systems behaviour,
    but we don't offer our users the ability understand what writeback is
    doing. There is no way to know how active it is over the whole system,
    if it's falling behind or to quantify it's efforts. With these values
    exported users can easily see how much data applications are sending
    through writeback and also at what rates writeback is processing this
    data. Comparing the rates of change between the two allow developers
    to see when writeback is not able to keep up with incoming traffic and
    the rate of dirty memory being sent to the IO back end. This allows
    folks to understand their io workloads and track kernel issues. Non
    kernel engineers at Google often use these counters to solve puzzling
    performance problems.

    Michael Rubin (2):
    mm: helper functions for dirty and writeback accounting
    writeback: Adding pages_dirtied and pages_entered_writeback

    Documentation/sysctl/vm.txt | 20 +++++++++++++++---
    drivers/base/node.c | 14 +++++++++++++
    fs/ceph/addr.c | 8 +-----
    fs/nilfs2/segment.c | 2 +-
    include/linux/mm.h | 1 +
    include/linux/mmzone.h | 2 +
    include/linux/writeback.h | 9 ++++++++
    kernel/sysctl.c | 14 +++++++++++++
    mm/page-writeback.c | 45 ++++++++++++++++++++++++++++++++++++++++--
    mm/vmstat.c | 2 +
    10 files changed, 103 insertions(+), 14 deletions(-)

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