* [PATCH] sched: Initialize rq->age_stamp on processor start
@ 2014-05-06 19:50 minyard
2014-05-08 16:13 ` Peter Zijlstra
0 siblings, 1 reply; 7+ messages in thread
From: minyard @ 2014-05-06 19:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: linux-kernel, Corey Minyard
From: Corey Minyard <cminyard@mvista.com>
If the sched_clock time starts at a large value, the kernel will spin
in sched_avg_update for a long time while rq->age_stamp catches up
with rq->clock.
The comment in kernel/sched/clock.c says that there is no strict promise
that it starts at zero. So initialize rq->age_stamp when a cpu starts up
to avoid this.
I was seeing long delays on a simulator that didn't start the clock at
zero. This might also be an issue on reboots on processors that don't
re-initialize the timer to zero on reset, and when using kexec.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
---
kernel/sched/core.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 268a45e..6e9570b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5039,11 +5039,20 @@ static struct notifier_block migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
+static void __cpuinit set_cpu_rq_start_time(void)
+{
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
+ rq->age_stamp = sched_clock_cpu(cpu);
+}
+
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_STARTING:
+ set_cpu_rq_start_time();
+ /* fall through */
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
@@ -6923,6 +6932,7 @@ void __init sched_init(void)
init_sched_fair_class();
scheduler_running = 1;
+ set_cpu_rq_start_time();
}
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
--
1.8.3.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] sched: Initialize rq->age_stamp on processor start
2014-05-06 19:50 [PATCH] sched: Initialize rq->age_stamp on processor start minyard
@ 2014-05-08 16:13 ` Peter Zijlstra
2014-05-08 18:47 ` Corey Minyard
2014-05-08 18:47 ` minyard
0 siblings, 2 replies; 7+ messages in thread
From: Peter Zijlstra @ 2014-05-08 16:13 UTC (permalink / raw)
To: minyard; +Cc: Ingo Molnar, linux-kernel, Corey Minyard
[-- Attachment #1: Type: text/plain, Size: 778 bytes --]
On Tue, May 06, 2014 at 02:50:57PM -0500, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> If the sched_clock time starts at a large value, the kernel will spin
> in sched_avg_update for a long time while rq->age_stamp catches up
> with rq->clock.
>
> The comment in kernel/sched/clock.c says that there is no strict promise
> that it starts at zero. So initialize rq->age_stamp when a cpu starts up
> to avoid this.
>
> I was seeing long delays on a simulator that didn't start the clock at
> zero. This might also be an issue on reboots on processors that don't
> re-initialize the timer to zero on reset, and when using kexec.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
This patch made my cris-defconfig build fail.
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] sched: Initialize rq->age_stamp on processor start
2014-05-08 16:13 ` Peter Zijlstra
@ 2014-05-08 18:47 ` Corey Minyard
2014-05-08 18:47 ` minyard
1 sibling, 0 replies; 7+ messages in thread
From: Corey Minyard @ 2014-05-08 18:47 UTC (permalink / raw)
To: Peter Zijlstra, minyard; +Cc: Ingo Molnar, linux-kernel
On 05/08/2014 11:13 AM, Peter Zijlstra wrote:
> On Tue, May 06, 2014 at 02:50:57PM -0500, minyard@acm.org wrote:
>> From: Corey Minyard <cminyard@mvista.com>
>>
>> If the sched_clock time starts at a large value, the kernel will spin
>> in sched_avg_update for a long time while rq->age_stamp catches up
>> with rq->clock.
>>
>> The comment in kernel/sched/clock.c says that there is no strict promise
>> that it starts at zero. So initialize rq->age_stamp when a cpu starts up
>> to avoid this.
>>
>> I was seeing long delays on a simulator that didn't start the clock at
>> zero. This might also be an issue on reboots on processors that don't
>> re-initialize the timer to zero on reset, and when using kexec.
>>
>> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> This patch made my cris-defconfig build fail.
Dang, I missed propagating a change. Yes, it's broken. One more time...
-corey
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] sched: Initialize rq->age_stamp on processor start
2014-05-08 16:13 ` Peter Zijlstra
2014-05-08 18:47 ` Corey Minyard
@ 2014-05-08 18:47 ` minyard
2014-05-09 9:12 ` Peter Zijlstra
` (2 more replies)
1 sibling, 3 replies; 7+ messages in thread
From: minyard @ 2014-05-08 18:47 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: linux-kernel, Corey Minyard
From: Corey Minyard <cminyard@mvista.com>
If the sched_clock time starts at a large value, the kernel will spin
in sched_avg_update for a long time while rq->age_stamp catches up
with rq->clock.
The comment in kernel/sched/clock.c says that there is no strict promise
that it starts at zero. So initialize rq->age_stamp when a cpu starts up
to avoid this.
I was seeing long delays on a simulator that didn't start the clock at
zero. This might also be an issue on reboots on processors that don't
re-initialize the timer to zero on reset, and when using kexec.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
---
kernel/sched/core.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 268a45e..80725c9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5039,11 +5039,20 @@ static struct notifier_block migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
+static void __cpuinit set_cpu_rq_start_time(void)
+{
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
+ rq->age_stamp = sched_clock_cpu(cpu);
+}
+
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_STARTING:
+ set_cpu_rq_start_time();
+ /* fall through */
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
@@ -6919,6 +6928,7 @@ void __init sched_init(void)
if (cpu_isolated_map == NULL)
zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
idle_thread_set_boot_cpu();
+ set_cpu_rq_start_time();
#endif
init_sched_fair_class();
--
1.8.3.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] sched: Initialize rq->age_stamp on processor start
2014-05-08 18:47 ` minyard
@ 2014-05-09 9:12 ` Peter Zijlstra
2014-05-19 13:10 ` [tip:sched/core] sched: Initialize rq-> age_stamp " tip-bot for Corey Minyard
2014-05-22 12:28 ` tip-bot for Corey Minyard
2 siblings, 0 replies; 7+ messages in thread
From: Peter Zijlstra @ 2014-05-09 9:12 UTC (permalink / raw)
To: minyard; +Cc: Ingo Molnar, linux-kernel, Corey Minyard
[-- Attachment #1: Type: text/plain, Size: 739 bytes --]
On Thu, May 08, 2014 at 01:47:39PM -0500, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> If the sched_clock time starts at a large value, the kernel will spin
> in sched_avg_update for a long time while rq->age_stamp catches up
> with rq->clock.
>
> The comment in kernel/sched/clock.c says that there is no strict promise
> that it starts at zero. So initialize rq->age_stamp when a cpu starts up
> to avoid this.
>
> I was seeing long delays on a simulator that didn't start the clock at
> zero. This might also be an issue on reboots on processors that don't
> re-initialize the timer to zero on reset, and when using kexec.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
Thanks
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^ permalink raw reply [flat|nested] 7+ messages in thread
* [tip:sched/core] sched: Initialize rq-> age_stamp on processor start
2014-05-08 18:47 ` minyard
2014-05-09 9:12 ` Peter Zijlstra
@ 2014-05-19 13:10 ` tip-bot for Corey Minyard
2014-05-22 12:28 ` tip-bot for Corey Minyard
2 siblings, 0 replies; 7+ messages in thread
From: tip-bot for Corey Minyard @ 2014-05-19 13:10 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, mingo, hpa, mingo, peterz, tglx, cminyard
Commit-ID: 6cfa0c323ca96b7f619932725bfc0de1e4a484fc
Gitweb: http://git.kernel.org/tip/6cfa0c323ca96b7f619932725bfc0de1e4a484fc
Author: Corey Minyard <cminyard@mvista.com>
AuthorDate: Thu, 8 May 2014 13:47:39 -0500
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 19 May 2014 22:02:41 +0900
sched: Initialize rq->age_stamp on processor start
If the sched_clock time starts at a large value, the kernel will spin
in sched_avg_update for a long time while rq->age_stamp catches up
with rq->clock.
The comment in kernel/sched/clock.c says that there is no strict promise
that it starts at zero. So initialize rq->age_stamp when a cpu starts up
to avoid this.
I was seeing long delays on a simulator that didn't start the clock at
zero. This might also be an issue on reboots on processors that don't
re-initialize the timer to zero on reset, and when using kexec.
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1399574859-11714-1-git-send-email-minyard@acm.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/sched/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 10d9b50..c134eb0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5089,10 +5089,20 @@ static struct notifier_block migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
+static void __cpuinit set_cpu_rq_start_time(void)
+{
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
+ rq->age_stamp = sched_clock_cpu(cpu);
+}
+
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_STARTING:
+ set_cpu_rq_start_time();
+ return NOTIFY_OK;
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
@@ -6970,6 +6980,7 @@ void __init sched_init(void)
if (cpu_isolated_map == NULL)
zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
idle_thread_set_boot_cpu();
+ set_cpu_rq_start_time();
#endif
init_sched_fair_class();
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:sched/core] sched: Initialize rq-> age_stamp on processor start
2014-05-08 18:47 ` minyard
2014-05-09 9:12 ` Peter Zijlstra
2014-05-19 13:10 ` [tip:sched/core] sched: Initialize rq-> age_stamp " tip-bot for Corey Minyard
@ 2014-05-22 12:28 ` tip-bot for Corey Minyard
2 siblings, 0 replies; 7+ messages in thread
From: tip-bot for Corey Minyard @ 2014-05-22 12:28 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, peterz, tglx, cminyard
Commit-ID: a803f0261bb2bb57aab5542af3174db43b2a3887
Gitweb: http://git.kernel.org/tip/a803f0261bb2bb57aab5542af3174db43b2a3887
Author: Corey Minyard <cminyard@mvista.com>
AuthorDate: Thu, 8 May 2014 13:47:39 -0500
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 22 May 2014 11:16:35 +0200
sched: Initialize rq->age_stamp on processor start
If the sched_clock time starts at a large value, the kernel will spin
in sched_avg_update for a long time while rq->age_stamp catches up
with rq->clock.
The comment in kernel/sched/clock.c says that there is no strict promise
that it starts at zero. So initialize rq->age_stamp when a cpu starts up
to avoid this.
I was seeing long delays on a simulator that didn't start the clock at
zero. This might also be an issue on reboots on processors that don't
re-initialize the timer to zero on reset, and when using kexec.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1399574859-11714-1-git-send-email-minyard@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f5605b6..da302ca 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5089,10 +5089,20 @@ static struct notifier_block migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
+static void __cpuinit set_cpu_rq_start_time(void)
+{
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
+ rq->age_stamp = sched_clock_cpu(cpu);
+}
+
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_STARTING:
+ set_cpu_rq_start_time();
+ return NOTIFY_OK;
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
@@ -6970,6 +6980,7 @@ void __init sched_init(void)
if (cpu_isolated_map == NULL)
zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
idle_thread_set_boot_cpu();
+ set_cpu_rq_start_time();
#endif
init_sched_fair_class();
^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-05-22 12:29 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-05-06 19:50 [PATCH] sched: Initialize rq->age_stamp on processor start minyard
2014-05-08 16:13 ` Peter Zijlstra
2014-05-08 18:47 ` Corey Minyard
2014-05-08 18:47 ` minyard
2014-05-09 9:12 ` Peter Zijlstra
2014-05-19 13:10 ` [tip:sched/core] sched: Initialize rq-> age_stamp " tip-bot for Corey Minyard
2014-05-22 12:28 ` tip-bot for Corey Minyard
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