Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756305AbZALUrS (ORCPT ); Mon, 12 Jan 2009 15:47:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752247AbZALUq7 (ORCPT ); Mon, 12 Jan 2009 15:46:59 -0500 Received: from mail.gmx.net ([213.165.64.20]:45177 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752783AbZALUq6 (ORCPT ); Mon, 12 Jan 2009 15:46:58 -0500 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX19mBdIQajRmPXJsNn1dz34b6Rrpm3JUUIjaoOc2Yr ZD3NGaUwtq4lMg Subject: [patch take 2] Re: [BUG] How to get real-time priority using idle priority From: Mike Galbraith To: Brian Rogers Cc: linux-kernel@vger.kernel.org, Ingo Molnar In-Reply-To: <1231765433.5789.35.camel@marge.simson.net> References: <4969D0D7.2060401@xyzw.org> <1231736941.6003.7.camel@marge.simson.net> <1231765433.5789.35.camel@marge.simson.net> Content-Type: text/plain Date: Mon, 12 Jan 2009 21:46:52 +0100 Message-Id: <1231793212.5940.2.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 X-FuHaFi: 0.44 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3182 Lines: 106 On Mon, 2009-01-12 at 14:03 +0100, Mike Galbraith wrote: > Would you mind trying the below? Or better, this more complete version. Impact: fix latency issues when SCHED_IDLE tasks are queued. Exclude SCHED_IDLE tasks from wakeup preemption, ensure that same will always be wakeup preempted, and exclude them from being buddies so they will only be selected via their vruntime. Per a tip from Peter Zijlstra, also scale migration vruntime adjustment to compensate for differences in min_vruntime advance rates. Reported-by: Brian Rogers Signed-off-by: Mike Galbraith kernel/sched.c | 19 +++++++++++++++++-- kernel/sched_fair.c | 22 ++++++++++++++++------ 2 files changed, 33 insertions(+), 8 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index deb5ac8..bdc0b38 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1888,8 +1888,23 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) schedstat_inc(p, se.nr_forced2_migrations); } #endif - p->se.vruntime -= old_cfsrq->min_vruntime - - new_cfsrq->min_vruntime; + if (old_cpu != new_cpu) { + s64 delta = p->se.vruntime - old_cfsrq->min_vruntime; + + /* + * min_vruntimes may be advancing at wildly different + * rates, so we must scale the delta accordingly. + */ + if (new_cfsrq->load.weight != old_cfsrq->load.weight) { + int negative = delta < 0; + + delta = negative ? -delta : delta; + delta = calc_delta_mine(delta, + new_cfsrq->load.weight, &old_cfsrq->load); + delta = negative ? -delta : delta; + } + p->se.vruntime = new_cfsrq->min_vruntime + delta; + } __set_task_cpu(p, new_cpu); } diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 8e1352c..500ed14 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1340,14 +1340,18 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) static void set_last_buddy(struct sched_entity *se) { - for_each_sched_entity(se) - cfs_rq_of(se)->last = se; + for_each_sched_entity(se) { + if (likely(task_of(se)->policy != SCHED_IDLE)) + 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; + for_each_sched_entity(se) { + if (likely(task_of(se)->policy != SCHED_IDLE)) + cfs_rq_of(se)->next = se; + } } /* @@ -1393,12 +1397,18 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/