From: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
Matthias Brugger <matthias.bgg@gmail.com>
Cc: <yj.chiang@mediatek.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Mark-PK Tsai <mark-pk.tsai@mediatek.com>,
<stable@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-mediatek@lists.infradead.org>
Subject: [PATCH 5.4] sched/rt: Disable RT_RUNTIME_SHARE by default
Date: Thu, 14 Jul 2022 15:30:52 +0800 [thread overview]
Message-ID: <20220714073055.15049-1-mark-pk.tsai@mediatek.com> (raw)
From: Daniel Bristot de Oliveira <bristot@redhat.com>
commit 2586af1ac187f6b3a50930a4e33497074e81762d upstream.
The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime
between CPUs, allowing a CPU to run a real-time task up to 100% of the
time while leaving more space for non-real-time tasks to run on the CPU
that lend rt_runtime.
The problem is that a CPU can easily borrow enough rt_runtime to allow
a spinning rt-task to run forever, starving per-cpu tasks like kworkers,
which are non-real-time by design.
This patch disables RT_RUNTIME_SHARE by default, avoiding this problem.
The feature will still be present for users that want to enable it,
though.
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Wei Wang <wvw@google.com>
Link: https://lkml.kernel.org/r/b776ab46817e3db5d8ef79175fa0d71073c051c7.1600697903.git.bristot@redhat.com
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Cc: stable@vger.kernel.org
---
kernel/sched/features.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 2410db5e9a35..66c74aa4753e 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -77,7 +77,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
SCHED_FEAT(RT_PUSH_IPI, true)
#endif
-SCHED_FEAT(RT_RUNTIME_SHARE, true)
+SCHED_FEAT(RT_RUNTIME_SHARE, false)
SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(ATTACH_AGE_LOAD, true)
--
2.18.0
WARNING: multiple messages have this Message-ID (diff)
From: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
Matthias Brugger <matthias.bgg@gmail.com>
Cc: <yj.chiang@mediatek.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Mark-PK Tsai <mark-pk.tsai@mediatek.com>,
<stable@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-mediatek@lists.infradead.org>
Subject: [PATCH 5.4] sched/rt: Disable RT_RUNTIME_SHARE by default
Date: Thu, 14 Jul 2022 15:30:52 +0800 [thread overview]
Message-ID: <20220714073055.15049-1-mark-pk.tsai@mediatek.com> (raw)
From: Daniel Bristot de Oliveira <bristot@redhat.com>
commit 2586af1ac187f6b3a50930a4e33497074e81762d upstream.
The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime
between CPUs, allowing a CPU to run a real-time task up to 100% of the
time while leaving more space for non-real-time tasks to run on the CPU
that lend rt_runtime.
The problem is that a CPU can easily borrow enough rt_runtime to allow
a spinning rt-task to run forever, starving per-cpu tasks like kworkers,
which are non-real-time by design.
This patch disables RT_RUNTIME_SHARE by default, avoiding this problem.
The feature will still be present for users that want to enable it,
though.
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Wei Wang <wvw@google.com>
Link: https://lkml.kernel.org/r/b776ab46817e3db5d8ef79175fa0d71073c051c7.1600697903.git.bristot@redhat.com
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Cc: stable@vger.kernel.org
---
kernel/sched/features.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 2410db5e9a35..66c74aa4753e 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -77,7 +77,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
SCHED_FEAT(RT_PUSH_IPI, true)
#endif
-SCHED_FEAT(RT_RUNTIME_SHARE, true)
+SCHED_FEAT(RT_RUNTIME_SHARE, false)
SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(ATTACH_AGE_LOAD, true)
--
2.18.0
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next reply other threads:[~2022-07-14 7:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 7:30 Mark-PK Tsai [this message]
2022-07-14 7:30 ` [PATCH 5.4] sched/rt: Disable RT_RUNTIME_SHARE by default Mark-PK Tsai
2022-07-15 14:14 ` Greg KH
2022-07-15 14:14 ` Greg KH
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