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    SubjectRe: [PATCH][RFC] dirty balancing for cgroups
    On Fri, 11 Jul 2008 14:59:26 +0900 (JST)
    yamamoto@valinux.co.jp (YAMAMOTO Takashi) wrote:

    > > > > - This looks simple but, could you merge this into memory resource controller ?
    > > >
    > > > why?
    > > >
    > > 3 points.
    > > 1. Is this useful if used alone ?
    >
    > it can be. why not?
    >
    > > 2. memcg requires this kind of feature, basically.
    > >
    > > 3. I wonder I need more work to make this work well under memcg.
    >
    > i'm not sure if i understand these points. can you explain a bit?
    >
    In my understanding, dirty_ratio is for helping memory (reclaim) subsystem.

    See comments in fs/page-writeback.c:: determin_dirtyable_memory()
    ==
    /*
    * Work out the current dirty-memory clamping and background writeout
    * thresholds.
    *
    * The main aim here is to lower them aggressively if there is a lot of mapped
    * memory around. To avoid stressing page reclaim with lots of unreclaimable
    * pages. It is better to clamp down on writers than to start swapping, and
    * performing lots of scanning.
    *
    * We only allow 1/2 of the currently-unmapped memory to be dirtied.
    *
    * We don't permit the clamping level to fall below 5% - that is getting rather
    * excessive.
    *
    * We make sure that the background writeout level is below the adjusted
    * clamping level.
    ==

    "To avoid stressing page reclaim with lots of unreclaimable pages"

    Then, I think memcg should support this for helping relcaim under memcg.

    > my patch penalizes heavy-writer cgroups as task_dirty_limit does
    > for heavy-writer tasks. i don't think that it's necessary to be
    > tied to the memory subsystem because i merely want to group writers.
    >
    Hmm, maybe what I need is different from this ;)
    Does not seem to be a help for memory reclaim under memcg.


    Thanks,
    -Kame



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