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    SubjectRe: [RFC 2/5] sched: Add CPU rate soft caps
    On Friday 26 May 2006 14:20, Peter Williams wrote:
    > This patch implements (soft) CPU rate caps per task as a proportion of a
    > single CPU's capacity expressed in parts per thousand. The CPU usage
    > of capped tasks is determined by using Kalman filters to calculate the
    > (recent) average lengths of the task's scheduling cycle and the time
    > spent on the CPU each cycle and taking the ratio of the latter to the
    > former. To minimize overhead associated with uncapped tasks these
    > statistics are not kept for them.
    > Notes:
    > 1. To minimize the overhead incurred when testing to skip caps processing
    > for uncapped tasks a new flag PF_HAS_CAP has been added to flags.

    [ot]I'm sorry to see an Australian adopt American spelling [/ot]

    > 3. Enforcement of caps is not as strict as it could be in order to
    > reduce the possibility of a task being starved of CPU while holding
    > an important system resource with resultant overall performance
    > degradation. In effect, all runnable capped tasks will get some amount
    > of CPU access every active/expired swap cycle. This will be most
    > apparent for small or zero soft caps.

    The array swap happens very frequently if there are nothing but heavily cpu
    bound tasks, which is not an infrequent workload. I doubt the zero caps are
    very effective in that environment.

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      Last update: 2006-05-26 12:52    [W:0.025 / U:5.960 seconds]
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