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    SubjectRe: [PATCH 0/3] VM throttling: avoid blocking occasional writers
    Hi,
    Thanks for your reply.

    >>3) Use "dirty_ratio" as the blocking ratio. And add
    >> "start_writeback_ratio", and start writeback at
    >> start_writeback_ratio(default:90) * dirty_ratio / 100 [%].
    >> In this way, specifying blocking ratio can be done in the same way
    >> as current kernel, but high/low watermark algorithm is enabled.
    >I like 3 better, it should make tuning behavior more precise.

    Then, what do you think of the following idea?

    (4) add `dirty_start_writeback_ratio' as percentage of memory,
    at which a generator of dirty pages itself starts writeback
    (that is, non-blocking ratio).

    In this way, `dirty_ratio' is used as the blocking ratio, so we don't
    need to modify the sysctl.conf etc. I think it's easier to understand
    for administrators of systems, because the interface is similar as
    `dirty_background_ratio' and`dirty_ratio.'

    If this is OK, I'll repost the patch.

    > You can make an argument for absolute values for writeback,
    > if my disk will only write 70MB/s I may only want 203 sec of
    > pending writes, regardless of available memory.

    To realize tuning with absolute values, I consider that we need to
    modify handling of `dirty_background_ratio,' `dirty_ratio' and so on as
    well as `dirty_start_writeback_ratio.' I think this should be done in
    another patch if this feature is required.

    Regards,
    --
    Tomoki Sekiyama
    Hitachi, Ltd., Systems Development Laboratory


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