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From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Bruno Goncalves <bgoncalv@redhat.com>
Cc: CKI Project <cki-project@redhat.com>,
	linux-kernel@vger.kernel.org, nathan@kernel.org,
	Memory Management <mm-qe@redhat.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453
Date: Fri, 30 Jul 2021 14:22:18 +0200	[thread overview]
Message-ID: <1ea2fa5c-ae81-2389-7f02-2227636582e4@arm.com> (raw)
In-Reply-To: <f5b4beb9-4e75-0f4e-da8b-b7ccc12fee68@arm.com>

On 29/07/2021 16:38, Dietmar Eggemann wrote:
> On 29/07/2021 14:36, Bruno Goncalves wrote:
>> On Wed, Jul 28, 2021 at 5:55 PM Dietmar Eggemann
>> <dietmar.eggemann@arm.com> wrote:
>>>
>>> On 28/07/2021 15:11, Bruno Goncalves wrote:
> 
> [...]
> 
>>> Can't reproduce it on my Juno (arm64) (slow-switching (scpi-cpufreq
>>> driver)).
>>
>> We seem to be able to reproduce this only on Ampere Altra machines,
>> specifically on mtjade and mtsnow cpus.
>>
>> # cpupower frequency-info
>> analyzing CPU 0:
>>   driver: cppc_cpufreq
>>   CPUs which run at the same hardware frequency: 0
>>   CPUs which need to have their frequency coordinated by software: 0
>>   maximum transition latency:  Cannot determine or is not supported.
>>   hardware limits: 1000 MHz - 2.80 GHz
>>   available cpufreq governors: conservative ondemand userspace
>> powersave performance schedutil
>>   current policy: frequency should be within 2.00 GHz and 2.80 GHz.
>>                   The governor "schedutil" may decide which speed to use
>>                   within this range.
>>   current CPU frequency: 1.55 GHz (asserted by call to hardware)
>>
>> # ps -eTo comm,pid,pri,class | grep sugov
>> sugov:0            1082 140 DLN
>> sugov:1            1085 140 DLN
>> ...
>> sugov:78           1319 140 DLN
>> sugov:79           1320 140 DLN
> 
> Thanks! In the meantime I got access to an Ampere Altra so I can try
> 5.14.0-rc1 later today.

The task causing this seem to be the new `cppc_fie` DL task introduced
by commit 1eb5dde674f5 "cpufreq: CPPC: Add support for frequency
invariance" in v5.14-rc1.

With `CONFIG_ACPI_CPPC_CPUFREQ_FIE=y` and schedutil cpufreq governor on
slow-switching system:

DL task curr=`sugov:X` makes p=`cppc_fie` migrate and since it is in
`non_contending` state, migrate_task_rq_dl() calls 

  sub_running_bw()->__sub_running_bw()->cpufreq_update_util()->
  rq_clock()->assert_clock_updated()

on p. 

Can you try this snippet? It should fix it.

--8<--

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: Fri, 30 Jul 2021 14:03:40 +0200
Subject: [PATCH] sched/deadline: Fix missing clock update in
 migrate_task_rq_dl()

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 kernel/sched/deadline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index aaacd6cfd42f..4920f498492f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1733,6 +1733,7 @@ static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused
 	 */
 	raw_spin_rq_lock(rq);
 	if (p->dl.dl_non_contending) {
+		update_rq_clock(rq);
 		sub_running_bw(&p->dl, &rq->dl);
 		p->dl.dl_non_contending = 0;
 		/*
-- 
2.25.1

WARNING: multiple messages have this Message-ID
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Bruno Goncalves <bgoncalv@redhat.com>
Cc: CKI Project <cki-project@redhat.com>,
	linux-kernel@vger.kernel.org, nathan@kernel.org,
	Memory Management <mm-qe@redhat.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453
Date: Fri, 30 Jul 2021 14:22:18 +0200	[thread overview]
Message-ID: <1ea2fa5c-ae81-2389-7f02-2227636582e4@arm.com> (raw)
In-Reply-To: <f5b4beb9-4e75-0f4e-da8b-b7ccc12fee68@arm.com>

On 29/07/2021 16:38, Dietmar Eggemann wrote:
> On 29/07/2021 14:36, Bruno Goncalves wrote:
>> On Wed, Jul 28, 2021 at 5:55 PM Dietmar Eggemann
>> <dietmar.eggemann@arm.com> wrote:
>>>
>>> On 28/07/2021 15:11, Bruno Goncalves wrote:
> 
> [...]
> 
>>> Can't reproduce it on my Juno (arm64) (slow-switching (scpi-cpufreq
>>> driver)).
>>
>> We seem to be able to reproduce this only on Ampere Altra machines,
>> specifically on mtjade and mtsnow cpus.
>>
>> # cpupower frequency-info
>> analyzing CPU 0:
>>   driver: cppc_cpufreq
>>   CPUs which run at the same hardware frequency: 0
>>   CPUs which need to have their frequency coordinated by software: 0
>>   maximum transition latency:  Cannot determine or is not supported.
>>   hardware limits: 1000 MHz - 2.80 GHz
>>   available cpufreq governors: conservative ondemand userspace
>> powersave performance schedutil
>>   current policy: frequency should be within 2.00 GHz and 2.80 GHz.
>>                   The governor "schedutil" may decide which speed to use
>>                   within this range.
>>   current CPU frequency: 1.55 GHz (asserted by call to hardware)
>>
>> # ps -eTo comm,pid,pri,class | grep sugov
>> sugov:0            1082 140 DLN
>> sugov:1            1085 140 DLN
>> ...
>> sugov:78           1319 140 DLN
>> sugov:79           1320 140 DLN
> 
> Thanks! In the meantime I got access to an Ampere Altra so I can try
> 5.14.0-rc1 later today.

The task causing this seem to be the new `cppc_fie` DL task introduced
by commit 1eb5dde674f5 "cpufreq: CPPC: Add support for frequency
invariance" in v5.14-rc1.

With `CONFIG_ACPI_CPPC_CPUFREQ_FIE=y` and schedutil cpufreq governor on
slow-switching system:

DL task curr=`sugov:X` makes p=`cppc_fie` migrate and since it is in
`non_contending` state, migrate_task_rq_dl() calls 

  sub_running_bw()->__sub_running_bw()->cpufreq_update_util()->
  rq_clock()->assert_clock_updated()

on p. 

Can you try this snippet? It should fix it.

--8<--

From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: Fri, 30 Jul 2021 14:03:40 +0200
Subject: [PATCH] sched/deadline: Fix missing clock update in
 migrate_task_rq_dl()

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 kernel/sched/deadline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index aaacd6cfd42f..4920f498492f 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1733,6 +1733,7 @@ static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused
 	 */
 	raw_spin_rq_lock(rq);
 	if (p->dl.dl_non_contending) {
+		update_rq_clock(rq);
 		sub_running_bw(&p->dl, &rq->dl);
 		p->dl.dl_non_contending = 0;
 		/*
-- 
2.25.1

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  reply	other threads:[~2021-07-30 12:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28 13:11 Bruno Goncalves
2021-07-28 15:55 ` Dietmar Eggemann
2021-07-29 12:36   ` Bruno Goncalves
2021-07-29 12:36     ` Bruno Goncalves
2021-07-29 14:38     ` Dietmar Eggemann
2021-07-29 14:38       ` Dietmar Eggemann
2021-07-30 12:22       ` Dietmar Eggemann [this message]
2021-07-30 12:22         ` Dietmar Eggemann
2021-07-30 15:23         ` Bruno Goncalves
2021-07-30 15:23           ` Bruno Goncalves
2021-08-02  8:43           ` Dietmar Eggemann
2021-08-02  8:43             ` Dietmar Eggemann

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