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    SubjectRe: [PATCH] cgroup: limit block I/O bandwidth
    * Andrea Righi <righiandr@users.sourceforge.net> [2008-01-24 14:48:01]:

    > Pavel Emelyanov wrote:
    > > Andrea Righi wrote:
    > >> Balbir Singh wrote:
    > >>> * Andrea Righi <righiandr@users.sourceforge.net> [2008-01-23 16:23:59]:
    > >>>
    > >>>> Probably tracking who dirtied the pages would be the best approach, but
    > >>>> we want also to reduce the overhead of this tracking. So, we should find
    > >>>> a smart way to track which cgroup dirtied the pages and then only when
    > >>>> the i/o scheduler dispatches the write requests of those pages, account
    > >>>> the i/o operations to the opportune cgroup. In this way throttling could
    > >>>> be done probably in __set_page_dirty() as well.
    > >>>>
    > >>> I think the OpenVZ controller works that way.
    > >> Well... looking at the code it seems that OpenVZ doesn't use this
    > >> strategy, instead performs UBC-based I/O accounting looking at the
    > >
    > > We do track the task (well - the beancounter) who made the page
    > > dirty and then use this context for async write scheduling.
    >
    > Interesting... now I see that task_io_account_write() takes a
    > "struct page *" as argument and the "struct page" has the beancounter
    > pointer.
    >
    > >
    > >> __set_page_dirty*() for writes and submit_bio() for reads. Then,
    > >> independently from accounting data, it uses per-UBC i/o priority model
    > >> that is mapped directly on the CFQ i/o priority model.
    > >
    > > Vasisly Tarasov (out I/O guru ;)) has already prepared an RFC patchset
    > > for Jens with group scheduler (for sync requests only) and is going to
    > > send it this or next week.
    > >
    >
    > Very good! I look forward for this patchset.
    >

    Excellent! Can't wait to test it.

    > Thanks,
    > -Andrea

    --
    Warm Regards,
    Balbir Singh
    Linux Technology Center
    IBM, ISTL


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