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    SubjectRe: [ckrm-tech] [RFC][PATCH] UBC: user resource beancounters
    On Mon, 2006-08-21 at 14:45 -0700, Chandra Seetharaman wrote:
    > On Mon, 2006-08-21 at 17:24 +0400, Kirill Korotaev wrote:
    > > Chandra Seetharaman wrote:
    > > > Kirill,
    > > >
    > > > Here are some concerns I have (as of now) w.r.t using UBC for resource
    > > > management (in the context of resource groups).
    > > >
    > > > - guarantee support is missing. I do not see any code to provide the
    > > > minimum amount of resource a group can get. It is important for
    > > > providing QoS. (In a different email you did mention guarantee, i am
    > > > referring it here for completeness).
    > > I mentioned a couple of times that this is a limited core functionality
    > > in this patch set.
    > > guarantees are implementable as a separate UBC parameters.
    > I will wait for oomguarpages patches :)
    > >
    > > > - Creation of a UBC and assignment of task to a UBC always happen in
    > > > the context of the task that is affected. I can understand it works in
    > > > OpenVZ environment, but IMO has issues if one wants it to be used for
    > > > basic resource management
    > > > - application needs to be changed to use this feature.
    > > > - System administrator does not have the control to assign tasks to a
    > > > UBC. Application does by itself.
    > > > - Assignment of task to a UBC need to be transparent to the
    > > > application.

    I agree with the above points. Just want to add that assignment of a
    task to a container may not be transparent to the application. For
    example it may hit some limits and some reclaim may happen...

    > > this is not 100% true.
    > > UBC itself doesn't prevent from changing context on the fly.
    > > But since this leads to part of resources to be charged to
    > > one UBC and another part to another UBC and so long and so
    > Let the controllers and the users worry about that part.

    I think as the tasks move around, it becomes very heavy to move all the
    pages belonging to previous container to a new container.

    > As I mentioned UBC might be perfect for container resource management,
    > but what I am talking for is resource management _without_ a container.

    Can you explain that part a bit more?

    > >
    > > > - No ability to maintain resource specific data in the controller.
    > > it's false. fields can be added to user_beancounter struct easily.
    > > and that's what our controllers do.
    > With the model of static array for resources (struct ubparm ub_parms
    > [UB_RESOURCES] in struct user_beancounter), it is not be possible to
    > attach _different_ "controller specific" information to each of the
    > entries.
    > I do not think it is good idea to add controller specific information of
    > _different_ controllers to the user_beancounter. Think of all the fields
    > it will have when all the numproc controller needs is just the basic 3-4
    > fields.

    IMO it is okay to add the fields whenever necessary as Kirill
    suggested. I think once the container subject gets baked a little more,
    the controllers will also get tightly coupled.

    > >
    > > > - No ability to get the list of tasks belonging to a UBC.
    > > it is not true. it can be read from /proc or system calls interface,
    > > just like the way one finds all tasks belonging to one user :)
    > >
    > > BTW, what is so valueable in this feature?
    > Again, it may not be useful for container type usages (you can probably
    > get the list from somewhere else, but for resource management it is
    > useful for sysadmins).

    I'm also debating about whether printing task information is really any
    useful. If a sysadm wants to get information about any particular task
    then that can come from /proc/<pid>/container Though container list
    will be one place where one can easily get the list of all the contained
    tasks (and other resources like files).

    > >
    > > > - For a system administrator name for identification of a UBC is
    > > > better than a number (uid).
    > > Have you any problems with pids, uids, gids and signals?
    > Again, in container land each UB is attached with a container hence no
    > issue.
    > In a non-container situation IMO it will be easier to manage/associate
    > "gold", "silver", "bronze", "plastic" groups than 0, 11, 83 and 113.
    > > It is a question of interface. I don't mind in changing UBC interface even
    > > to configfs if someone really wants it.
    > >

    Yes please. Thanks.

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