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    SubjectRe: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)
    Pavel Emelianov wrote:
    > Kirill Korotaev wrote:
    > [snip]
    >>> I have a C program that computes limits to obtain desired guarantees
    >>> in a single 'for (i = 0; i < n; n++)' loop for any given set of guarantees.
    >>> With all error handling, beautifull output, nice formatting etc it weights
    >>> only 60 lines.
    > Look at
    > I've described there how a guarantee can be get with limiting in details.
    > [snip]
    >>> I do not 'do not like guarantee'. I'm just sure that there are two ways
    >>> for providing guarantee (for unreclaimable resorces):
    >>> 1. reserving resource for group in advance
    >>> 2. limit resource for others
    >>> Reserving is worse as it is essentially limiting (you cut off 100Mb from
    >>> 1Gb RAM thus limiting the other groups by 900Mb RAM), but this limiting
    >>> is too strict - you _have_ to reserve less than RAM size. Limiting in
    >>> run-time is more flexible (you may create an overcommited BC if you
    >>> want to) and leads to the same result - guarantee.
    >> I think this deserves putting on Wiki.
    >> It is very good clear point.
    > This is also on the page I gave link at.

    This approach has the following disadvantages
    1. Lets consider initialization - When we create 'n' groups initially, we need
    to spend O(n^2) time to assign guarantees.
    2. Every time a limit or a guarantee changes, we need to recalculate guarantees
    and ensure that the change will not break any guarantees
    3. The same thing as stated above, when a resource group is created or deleted

    This can lead to some instability; a change in one group propagates to all other groups.


    Balbir Singh,
    Linux Technology Center,
    IBM Software Labs
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      Last update: 2006-09-18 10:29    [W:0.043 / U:1.196 seconds]
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