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    SubjectRe: [PATCH][RFC] dirty balancing for cgroups
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    hi,

    > On Wed, 6 Aug 2008 17:20:46 +0900 (JST)
    > yamamoto@valinux.co.jp (YAMAMOTO Takashi) wrote:
    >
    > > hi,
    > >
    > > > On Fri, 11 Jul 2008 17:34:46 +0900 (JST)
    > > > yamamoto@valinux.co.jp (YAMAMOTO Takashi) wrote:
    > > >
    > > > > hi,
    > > > >
    > > > > > > 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.
    > > > >
    > > > > to implement what you need, i think that we need to keep track of
    > > > > the numbers of dirty-pages in each memory cgroups as a first step.
    > > > > do you agree?
    > > > >
    > > > yes, I think so, now.
    > > >
    > > > may be not difficult but will add extra overhead ;( Sigh..
    > >
    > > the following is a patch to add the overhead. :)
    > > any comments?
    > >
    > Do you have some numbers ? ;)

    not yet.

    > I like this because this seems very straightforward. thank you.

    good to hear.

    > How about changing these to be
    >
    > ==
    > void mem_cgroup_test_set_page_dirty()
    > {
    > if (try_lock_page_cgroup(pg)) {
    > pc = page_get_page_cgroup(pg);
    > if (pc ......) {
    > }
    > unlock_page_cgroup(pg)
    > }
    > }
    > ==

    i'm not sure how many opportunities to update statistics
    we would lose for the trylock failure.
    although the statistics don't need to be too precise,
    its error should have a reasonable upper-limit to be useful.

    > Off-topic: I wonder we can delete this "lock" in future.
    >
    > Because page->page_cgroup is
    > 1. attached at first use.(Obiously no race with set_dirty)
    > 2. deleted at removal. (force_empty is problematic here..)

    i hope it's possible. :)

    YAMAMOTO Takashi

    >
    > But, now, we need this lock.
    >
    > Thanks,
    > -Kame
    >
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