--- linux-2.6.1/kernel/sched.c 2004-01-27 16:31:25.943252960 +1100 +++ linux-2.6.1-ck1/kernel/sched.c 2004-01-27 16:31:41.487889816 +1100 @@ -1164,8 +1164,9 @@ can_migrate_task(task_t *tsk, runqueue_t { unsigned long delta = sched_clock() - tsk->timestamp; - if (!idle && (delta <= JIFFIES_TO_NS(cache_decay_ticks))) - return 0; + if (!idle && (delta <= JIFFIES_TO_NS(cache_decay_ticks)) && + !ht_siblings(this_cpu, task_cpu(tsk))) + return 0; if (task_running(rq, tsk)) return 0; if (!cpu_isset(this_cpu, tsk->cpus_allowed)) @@ -1200,15 +1201,23 @@ static void load_balance(runqueue_t *thi imbalance /= 2; /* + * For hyperthread siblings take tasks from the active array + * to get cache-warm tasks since they share caches. + */ + if (ht_siblings(this_cpu, busiest->cpu)) + array = busiest->active; + /* * We first consider expired tasks. Those will likely not be * executed in the near future, and they are most likely to * be cache-cold, thus switching CPUs has the least effect * on them. */ - if (busiest->expired->nr_active) - array = busiest->expired; - else - array = busiest->active; + else { + if (busiest->expired->nr_active) + array = busiest->expired; + else + array = busiest->active; + } new_array: /* Start searching at priority 0: */ @@ -1219,9 +1228,16 @@ skip_bitmap: else idx = find_next_bit(array->bitmap, MAX_PRIO, idx); if (idx >= MAX_PRIO) { - if (array == busiest->expired) { - array = busiest->active; - goto new_array; + if (ht_siblings(this_cpu, busiest->cpu)){ + if (array == busiest->active) { + array = busiest->expired; + goto new_array; + } + } else { + if (array == busiest->expired) { + array = busiest->active; + goto new_array; + } } goto out_unlock; }