Messages in this thread Patch in this message | | | Date | Tue, 25 Apr 2006 13:08:00 +1000 | From | Peter Williams <> | Subject | [PATCH] sched: fix evaluation of skip_for_load in move_tasks() |
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Problem:
In the patch sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks.patch I got a the sense of a boolean expression wrong when assigning a value to skip_for_load. The expression should have been negated before being assigned.
Additionally, busiest_best_prio_seen is being set when tasks are moved instead of when they are skipped which will cause problems when the current task does not have prio=busiest_best_prio.
Solution:
Negate the expression and apply de Marcos rule to simplify it and move the setting of busiest_best_prio_seen.
This patch is on top of sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks.patch
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
-- Peter Williams pwil3058@bigpond.net.au
"Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce Index: MM-2.6.17-rc1-mm3/kernel/sched.c =================================================================== --- MM-2.6.17-rc1-mm3.orig/kernel/sched.c 2006-04-25 12:53:39.000000000 +1000 +++ MM-2.6.17-rc1-mm3/kernel/sched.c 2006-04-25 12:56:14.000000000 +1000 @@ -2059,7 +2059,10 @@ static int move_tasks(runqueue_t *this_r busiest_best_prio = rq_best_prio(busiest); /* * Enable handling of the case where there is more than one task - * with the best priority. + * with the best priority. If the current running task is one + * of those with prio==busiest_best_prio we know it won't be moved + * and therefore it's safe to override the skip (based on load) of + * any task we find with that prio. */ busiest_best_prio_seen = busiest_best_prio == busiest->curr->prio; @@ -2108,9 +2111,10 @@ skip_queue: */ skip_for_load = tmp->load_weight > rem_load_move; if (skip_for_load && idx < this_best_prio) - skip_for_load = busiest_best_prio_seen || idx != busiest_best_prio; + skip_for_load = !busiest_best_prio_seen && idx == busiest_best_prio; if (skip_for_load || !can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) { + busiest_best_prio_seen |= idx == busiest_best_prio; if (curr != head) goto skip_queue; idx++; @@ -2133,8 +2137,6 @@ skip_queue: if (pulled < max_nr_move && rem_load_move > 0) { if (idx < this_best_prio) this_best_prio = idx; - if (idx == busiest_best_prio) - busiest_best_prio_seen = 1; if (curr != head) goto skip_queue; idx++; | |