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    SubjectRe: [PATCH 0/6 v4] cfq-iosched: Introduce CFQ group hierarchical scheduling and "use_hierarchy" interface
    On Sat, Feb 12, 2011 at 02:08:54PM +0800, Gui Jianfeng wrote:
    > Vivek Goyal wrote:
    > > On Thu, Feb 10, 2011 at 03:45:45PM +0800, Gui Jianfeng wrote:
    > >> Hi
    > >>
    > >> Previously, I posted a patchset to add support of CFQ group hierarchical scheduling
    > >> in the way that it puts all CFQ queues in a hidden group and schedules with other
    > >> CFQ group under their parent. The patchset is available here,
    > >>
    > >>
    > >> Vivek think this approach isn't so instinct that we should treat CFQ queues
    > >> and groups at the same level. Here is the new approach for hierarchical
    > >> scheduling based on Vivek's suggestion. The most big change of CFQ is that
    > >> it gets rid of cfq_slice_offset logic, and makes use of vdisktime for CFQ
    > >> queue scheduling just like CFQ group does. But I still give cfqq some jump
    > >> in vdisktime based on ioprio, thanks for Vivek to point out this. Now CFQ
    > >> queue and CFQ group use the same scheduling algorithm.
    > >>
    > >> "use_hierarchy" interface is now added to switch between hierarchical mode
    > >> and flat mode. It works as memcg.
    > >>
    > >> --
    > >> V3 -> V4 Changes:
    > >> - Take io class into account when calculating the boost value.
    > >> - Refine the vtime boosting logic as Vivek's Suggestion.
    > >
    > > Hi Gui,
    > >
    > > What testing did you do to make sure that this vtime boosting logic is working
    > > and is good replacement for slice_offset() logic for cfqq?
    > >
    > > Secondly, did you get a chance to look at chad's patch of keeping track
    > > of previous assigned vdisktime and keeping track of genrations. I think
    > > his patch is going to coflict with yours, so one of you will have to
    > > make adjustments. I think both the boost logic and keeping track of generation
    > > logic can be combined.
    > Hi Vivek,
    > For the time being, boosting logic only works for cfq queue, and keepinging track of
    > generation works for cfq group.
    > I think when we introduce boosting logic for cfq group, we can combine these two logic
    > together.

    Ok, I am assuming that now you are introducing another patch in the series
    to get boosting logic working for groups also.

    Also, it might be easier to test it with group_idle=0, as right now groups
    don't preempt each other.


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