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UPSTREAM: sched/rt: Disable RT_RUNTIME_SHARE by default

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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
(cherry picked from commit 2586af1ac187f6b3a50930a4e33497074e81762d)
Change-Id: Ibb1b185d512130783ac9f0a29f0e20e9828c86fd

Bug: 169673278
Test: build, boot and check the trace with RT task
Signed-off-by: Kyle Lin <kylelin@google.com>
Change-Id: Iffede8107863b02ad4a0cb902fc8119416931bdb
This commit is contained in:
Daniel Bristot de Oliveira 2020-09-21 16:39:49 +02:00 committed by spakkkk
parent a1460afbc4
commit fdab3bbf27
1 changed files with 1 additions and 1 deletions
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kernel/sched/features.h
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@ -78,7 +78,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
SCHED_FEAT(RT_PUSH_IPI, true) SCHED_FEAT(RT_PUSH_IPI, true)
#endif #endif
SCHED_FEAT(RT_RUNTIME_SHARE, true) SCHED_FEAT(RT_RUNTIME_SHARE, false)
SCHED_FEAT(LB_MIN, false) SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(ATTACH_AGE_LOAD, true) SCHED_FEAT(ATTACH_AGE_LOAD, true)