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    SubjectRe: [RFC][PATCH 4/7][memcg] memcg use ID in page_cgroup
    On Tue, 27 Jul 2010 23:13:58 -0400
    Vivek Goyal <vgoyal@redhat.com> wrote:

    > > > So the idea is that when a page is allocated, also store the blk_group
    > > > id and once that page is submitted for writeback, we should be able
    > > > to associate it to right blkio group?
    > > >
    > > blk_cgroup id can be attached whenever you wants. please overwrite
    > > page_cgroup->blk_cgroup when it's necessary.
    >
    > > Did you read Ikeda's patch ? I myself doesn't have patches at this point.
    > > This is just for make a room for recording blkio-ID, which was requested
    > > for a year.
    >
    > I have not read his patches yet. IIRC, previously there were issues
    > regarding which group should be charged for the page. The person who
    > allocated it or the thread which did last write to it etc... I guess
    > we can sort that out later.
    >
    > >
    > > Hmm, but page-allocation-time doesn't sound very good for me.
    > >
    >
    > Why?
    >

    As you wrote, by attaching ID when a page cache is added, we'll have
    much chances of free-rider until it's paged out. So, adding some
    reseting-owner point may be good.

    But considering real world usage, I may be wrong.
    There will not be much free rider in real world, especially at write().
    Then, page-allocation time may be good.

    (Because database doesn't use page-cache, there will be no big random write
    application.)

    Thanks,
    -Kame



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