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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>
Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com>,
	Mike Galbraith <efault@gmx.de>,
	Dhaval Giani <dhaval@linux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [RFC/PATCH 05/17] sched: rt-group: optimize dequeue_rt_stack
Date: Sun, 09 Mar 2008 18:08:55 +0100	[thread overview]
Message-ID: <20080309170926.855392000@chello.nl> (raw)
In-Reply-To: <20080309170850.256853000@chello.nl>

[-- Attachment #1: sched-rt-group-opt-dequeue.patch --]
[-- Type: text/plain, Size: 1886 bytes --]

Now that the group hierarchy can have an arbitrary depth the O(n^2) nature
of RT task dequeues will really hurt. Optimize this by providing space to
store the tree path, so we can walk it the other way.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/sched.h |    1 +
 kernel/sched_rt.c     |   28 ++++++++++++----------------
 2 files changed, 13 insertions(+), 16 deletions(-)

Index: linux-2.6-2/kernel/sched_rt.c
===================================================================
--- linux-2.6-2.orig/kernel/sched_rt.c
+++ linux-2.6-2/kernel/sched_rt.c
@@ -479,26 +479,22 @@ static void dequeue_rt_entity(struct sch
 /*
  * Because the prio of an upper entry depends on the lower
  * entries, we must remove entries top - down.
- *
- * XXX: O(1/2 h^2) because we can only walk up, not down the chain.
  */
 static void dequeue_rt_stack(struct task_struct *p)
 {
-	struct sched_rt_entity *rt_se, *top_se;
+	struct sched_rt_entity *rt_se, *back = NULL;
 
-	/*
-	 * dequeue all, top - down.
-	 */
-	do {
-		rt_se = &p->rt;
-		top_se = NULL;
-		for_each_sched_rt_entity(rt_se) {
-			if (on_rt_rq(rt_se))
-				top_se = rt_se;
-		}
-		if (top_se)
-			dequeue_rt_entity(top_se);
-	} while (top_se);
+	rt_se = &p->rt;
+	for_each_sched_rt_entity(rt_se) {
+		if (!on_rt_rq(rt_se))
+			break;
+
+		rt_se->back = back;
+		back = rt_se;
+	}
+
+	for (rt_se = back; rt_se; rt_se = rt_se->back)
+		dequeue_rt_entity(rt_se);
 }
 
 /*
Index: linux-2.6-2/include/linux/sched.h
===================================================================
--- linux-2.6-2.orig/include/linux/sched.h
+++ linux-2.6-2/include/linux/sched.h
@@ -978,6 +978,7 @@ struct sched_rt_entity {
 	unsigned long timeout;
 	int nr_cpus_allowed;
 
+	struct sched_rt_entity *back;
 #ifdef CONFIG_RT_GROUP_SCHED
 	struct sched_rt_entity	*parent;
 	/* rq on which this entity is (to be) queued: */

--


  parent reply	other threads:[~2008-03-09 17:12 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-09 17:08 [RFC/PATCH 00/17] Current sched patch stack Peter Zijlstra
2008-03-09 17:08 ` [RFC/PATCH 01/17] sched: mix tasks and groups Peter Zijlstra
2008-04-01 12:12   ` Srivatsa Vaddagiri
2008-04-01 12:05     ` Peter Zijlstra
2008-03-09 17:08 ` [RFC/PATCH 02/17] sched: allow the CFS group scheduler to have multiple levels Peter Zijlstra
2008-03-12 14:47   ` Dhaval Giani
2008-03-09 17:08 ` [RFC/PATCH 03/17] sched: rt-group: full hierarchy support for the rt groups Peter Zijlstra
2008-03-12  8:25   ` Dhaval Giani
     [not found]     ` <661de9470803120129l66497656o948c13c6c0c26766@mail.gmail.com>
2008-03-12  9:29       ` Peter Zijlstra
2008-03-12 13:34         ` Balbir Singh
2008-03-12 13:39           ` Dhaval Giani
2008-03-12 14:08         ` Balbir Singh
2008-03-09 17:08 ` [RFC/PATCH 04/17] sched: fair-group: SMP-nice for group scheduling Peter Zijlstra
2008-03-09 17:08 ` Peter Zijlstra [this message]
2008-03-09 17:08 ` [RFC/PATCH 06/17] sched: fair-group scheduling vs latency Peter Zijlstra
2008-03-09 17:08 ` [RFC/PATCH 07/17] sched: fair-group: de-couple load-balancing from the rb-trees Peter Zijlstra
2008-03-09 17:08 ` [RFC/PATCH 08/17] sched: fair-group: single RQ approach Peter Zijlstra
2008-03-09 17:08 ` [RFC/PATCH 09/17] sched: fair: remove moved_group() Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 10/17] sched: remove sysctl_sched_batch_wakeup_granularity Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 11/17] sched: fair: optimize sched_slice() Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 12/17] sched: fair: cfs_root_rq Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 13/17] sched: fair: calc_delta_weight() Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 14/17] sched: fair: avg_vruntime Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 15/17] sched: fair-group: EEVDF scheduling Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 16/17] sched: fair: bound tardiness Peter Zijlstra
2008-03-09 17:09 ` [RFC/PATCH 17/17] sched: fair: optimize the elegebility test Peter Zijlstra

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