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    SubjectRe: IO scheduler based IO Controller V2
    Ryo Tsuruta wrote:
    > Hi Vivek,
    >
    >> Ryo, dm-ioband breaks the notion of classes and priority of CFQ because
    >> of FIFO dispatch of buffered bios. Apart from that it tries to provide
    >> fairness in terms of actual IO done and that would mean a seeky workload
    >> will can use disk for much longer to get equivalent IO done and slow down
    >> other applications. Implementing IO controller at IO scheduler level gives
    >> us tigher control. Will it not meet your requirements? If you got specific
    >> concerns with IO scheduler based contol patches, please highlight these and
    >> we will see how these can be addressed.
    >
    > I'd like to avoid making complicated existing IO schedulers and other
    > kernel codes and to give a choice to users whether or not to use it.
    > I know that you chose an approach that using compile time options to
    > get the same behavior as old system, but device-mapper drivers can be
    > added, removed and replaced while system is running.

    I do not believe that every use of cgroups will end up with
    a separate logical volume for each group.

    In fact, if you look at group-per-UID usage, which could be
    quite common on shared web servers and shell servers, I would
    expect all the groups to share the same filesystem.

    I do not believe dm-ioband would be useful in that configuration,
    while the IO scheduler based IO controller will just work.

    --
    All rights reversed.


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