sched: fix MC/HT scheduler optimization, without breaking the FUZZ logic.
First fix the check if (*imbalance + SCHED_LOAD_SCALE_FUZZ < busiest_load_per_task) with this if (*imbalance < busiest_load_per_task) As the current check is always false for nice 0 tasks (as SCHED_LOAD_SCALE_FUZZ is same as busiest_load_per_task for nice 0 tasks). With the above change, imbalance was getting reset to 0 in the corner case condition, making the FUZZ logic fail. Fix it by not corrupting the imbalance and change the imbalance, only when it finds that the HT/MC optimization is needed. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 changed files with 3 additions and 5 deletions
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@ -2512,7 +2512,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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* a think about bumping its value to force at least one task to be
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* moved
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*/
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if (*imbalance + SCHED_LOAD_SCALE_FUZZ < busiest_load_per_task) {
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if (*imbalance < busiest_load_per_task) {
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unsigned long tmp, pwr_now, pwr_move;
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unsigned int imbn;
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@ -2564,10 +2564,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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pwr_move /= SCHED_LOAD_SCALE;
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/* Move if we gain throughput */
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if (pwr_move <= pwr_now)
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goto out_balanced;
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*imbalance = busiest_load_per_task;
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if (pwr_move > pwr_now)
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*imbalance = busiest_load_per_task;
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}
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return busiest;
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