From f1adad78dd2fc8edaa513e0bde92b4c64340245c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 21 May 2006 18:54:09 -0700 Subject: Revert "[PATCH] sched: fix interactive task starvation" This reverts commit 5ce74abe788a26698876e66b9c9ce7e7acc25413 (and its dependent commit 8a5bc075b8d8cf7a87b3f08fad2fba0f5d13295e), because of audio underruns. Reported by Rene Herman , who also pinpointed the exact cause of the underruns: "Audio underruns galore, with only ogg123 and firefox (browsing the GIT tree online is also a nice trigger by the way). If I back it out, everything is fine for me again." Cc: Rene Herman Cc: Mike Galbraith Acked-by: Con Kolivas Signed-off-by: Linus Torvalds --- kernel/sched.c | 62 +++++++++++++++++----------------------------------------- 1 file changed, 18 insertions(+), 44 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 4c64f85698ae..c13f1bd2df7d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -664,48 +664,6 @@ static int effective_prio(task_t *p) return prio; } -/* - * We place interactive tasks back into the active array, if possible. - * - * To guarantee that this does not starve expired tasks we ignore the - * interactivity of a task if the first expired task had to wait more - * than a 'reasonable' amount of time. This deadline timeout is - * load-dependent, as the frequency of array switched decreases with - * increasing number of running tasks. We also ignore the interactivity - * if a better static_prio task has expired, and switch periodically - * regardless, to ensure that highly interactive tasks do not starve - * the less fortunate for unreasonably long periods. - */ -static inline int expired_starving(runqueue_t *rq) -{ - int limit; - - /* - * Arrays were recently switched, all is well - */ - if (!rq->expired_timestamp) - return 0; - - limit = STARVATION_LIMIT * rq->nr_running; - - /* - * It's time to switch arrays - */ - if (jiffies - rq->expired_timestamp >= limit) - return 1; - - /* - * There's a better selection in the expired array - */ - if (rq->curr->static_prio > rq->best_expired_prio) - return 1; - - /* - * All is well - */ - return 0; -} - /* * __activate_task - move a task to the runqueue. */ @@ -713,7 +671,7 @@ static void __activate_task(task_t *p, runqueue_t *rq) { prio_array_t *target = rq->active; - if (unlikely(batch_task(p) || (expired_starving(rq) && !rt_task(p)))) + if (batch_task(p)) target = rq->expired; enqueue_task(p, target); rq->nr_running++; @@ -2531,6 +2489,22 @@ unsigned long long current_sched_time(const task_t *tsk) return ns; } +/* + * We place interactive tasks back into the active array, if possible. + * + * To guarantee that this does not starve expired tasks we ignore the + * interactivity of a task if the first expired task had to wait more + * than a 'reasonable' amount of time. This deadline timeout is + * load-dependent, as the frequency of array switched decreases with + * increasing number of running tasks. We also ignore the interactivity + * if a better static_prio task has expired: + */ +#define EXPIRED_STARVING(rq) \ + ((STARVATION_LIMIT && ((rq)->expired_timestamp && \ + (jiffies - (rq)->expired_timestamp >= \ + STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \ + ((rq)->curr->static_prio > (rq)->best_expired_prio)) + /* * Account user cpu time to a process. * @p: the process that the cpu time gets accounted to @@ -2666,7 +2640,7 @@ void scheduler_tick(void) if (!rq->expired_timestamp) rq->expired_timestamp = jiffies; - if (!TASK_INTERACTIVE(p) || expired_starving(rq)) { + if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) { enqueue_task(p, rq->expired); if (p->static_prio < rq->best_expired_prio) rq->best_expired_prio = p->static_prio; -- cgit v1.2.2