Re: [PATCH] Fix find busiest queue 2.6.0-test9

[Nick Piggin]

Martin J. Bligh wrote:

> On the same vein ... this looks odd:
>
>         * We fend off statistical fluctuations in runqueue lengths by
>         * saving the runqueue length during the previous load-balancing
>         * operation and using the smaller one the current and saved lengths.
>         * If a runqueue is long enough for a longer amount of time then
>         * we recognize it and pull tasks from it.
> ...
>        if (idle || (this_rq->nr_running > this_rq->prev_cpu_load[this_cpu]))
>                nr_running = this_rq->nr_running;
>        else
>                nr_running = this_rq->prev_cpu_load[this_cpu];
>
> It says we uses the smaller of the two in the comment, but then it seems to
> use the > of the two in the code? Unless I'm losing it, which is likely ;-)

You want the larger of the two values to be taken for the destination
queue, and the smaller to be taken for the source queue. This way you
get a minimal imbalance.


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