Messages in this thread Patch in this message | | | Date | Wed, 18 Feb 2009 13:32:30 -0800 | From | Greg KH <> | Subject | [patch 09/39] sched: SCHED_OTHER vs SCHED_IDLE isolation |
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2.6.28-stable review patch. If anyone has any objections, please let us know.
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
commit 6bc912b71b6f33b041cfde93ca3f019cbaa852bc upstream.
Stronger SCHED_IDLE isolation:
- no SCHED_IDLE buddies - never let SCHED_IDLE preempt on wakeup - always preempt SCHED_IDLE on wakeup - limit SLEEPER fairness for SCHED_IDLE.
Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/sched_fair.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-)
--- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -681,9 +681,13 @@ place_entity(struct cfs_rq *cfs_rq, stru unsigned long thresh = sysctl_sched_latency; /* - * convert the sleeper threshold into virtual time + * Convert the sleeper threshold into virtual time. + * SCHED_IDLE is a special sub-class. We care about + * fairness only relative to other SCHED_IDLE tasks, + * all of which have the same weight. */ - if (sched_feat(NORMALIZED_SLEEPER)) + if (sched_feat(NORMALIZED_SLEEPER) && + task_of(se)->policy != SCHED_IDLE) thresh = calc_delta_fair(thresh, se); vruntime -= thresh; @@ -1328,14 +1332,18 @@ wakeup_preempt_entity(struct sched_entit static void set_last_buddy(struct sched_entity *se) { - for_each_sched_entity(se) - cfs_rq_of(se)->last = se; + if (likely(task_of(se)->policy != SCHED_IDLE)) { + for_each_sched_entity(se) + cfs_rq_of(se)->last = se; + } } static void set_next_buddy(struct sched_entity *se) { - for_each_sched_entity(se) - cfs_rq_of(se)->next = se; + if (likely(task_of(se)->policy != SCHED_IDLE)) { + for_each_sched_entity(se) + cfs_rq_of(se)->next = se; + } } /* @@ -1382,12 +1390,18 @@ static void check_preempt_wakeup(struct return; /* - * Batch tasks do not preempt (their preemption is driven by + * Batch and idle tasks do not preempt (their preemption is driven by * the tick): */ - if (unlikely(p->policy == SCHED_BATCH)) + if (unlikely(p->policy != SCHED_NORMAL)) return; + /* Idle tasks are by definition preempted by everybody. */ + if (unlikely(curr->policy == SCHED_IDLE)) { + resched_task(curr); + return; + } + if (!sched_feat(WAKEUP_PREEMPT)) return;
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