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Date: Tue, 17 Feb 2009 07:46:51 +0100
From: Mike Galbraith <efault@....de>
To: John Werden <jwerden@...pop.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [BUG] SCHED_IDLE makes system unresponsive
Hi,
On Mon, 2009-02-16 at 20:55 +0100, John Werden wrote:
> I use a file indexer program named pinot and the newest versions of
> it seem to freeze my system (completely unresponsive X Server/GUI,
> frozen mouse pointer, no hdd activity). I could track the problem down
> to a single commit, which makes pinot use SCHED_IDLE instead of
> priority 15:
>
> http://svn.berlios.de/wsvn/pinot/?op=comp&compare[]=%2F@...7&compare[]=%2F@...8
>
> I also found out that the problem is already known on the mailing
> list, but I don't know if it was solved with the following commit in
> 2.6.28.2:
>
> http://lkml.org/lkml/2009/1/22/416
>
> other related threads I found:
>
> http://lkml.org/lkml/2009/1/11/70
> http://lkml.org/lkml/2009/1/30/297
>
> Is this correct? I use 2.6.28.5 and still encounter the problem (I
> didn't test it with earlier kernel versions). How can I work around this
> or/and make SCHED_IDLE work as intended? It looks like right now every
> running program could freeze my system which I definitely don't want.
If you need to use SCHED_IDLE in 28-stable, you'll want the below.
commit 6bc912b71b6f33b041cfde93ca3f019cbaa852bc
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Thu Jan 15 14:53:38 2009 +0100
sched: SCHED_OTHER vs SCHED_IDLE isolation
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@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/sched_fair.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
Index: linux-2.6.28/kernel/sched_fair.c
===================================================================
--- linux-2.6.28.orig/kernel/sched_fair.c
+++ linux-2.6.28/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;
+ }
}
/*
@@ -1382,11 +1390,17 @@ 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;
commit cce7ade803699463ecc62a065ca522004f7ccb3d
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Thu Jan 15 14:53:37 2009 +0100
sched: SCHED_IDLE weight change
Increase the SCHED_IDLE weight from 2 to 3, this gives much more stable
vruntime numbers.
time advanced in 100ms:
weight=2
64765.988352
67012.881408
88501.412352
weight=3
35496.181411
34130.971298
35497.411573
Signed-off-by: Mike Galbraith <efault@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/sched.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Index: linux-2.6.28/kernel/sched.c
===================================================================
--- linux-2.6.28.orig/kernel/sched.c
+++ linux-2.6.28/kernel/sched.c
@@ -1314,8 +1314,8 @@ static inline void update_load_sub(struc
* slice expiry etc.
*/
-#define WEIGHT_IDLEPRIO 2
-#define WMULT_IDLEPRIO (1 << 31)
+#define WEIGHT_IDLEPRIO 3
+#define WMULT_IDLEPRIO 1431655765
/*
* Nice levels are multiplicative, with a gentle 10% change for every
--
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