Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 136 insertions, 0 deletions

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
new file mode 100644
index 000000000..c2f1fd95a
--- /dev/null
+++ b/kernel/Kconfig.preempt
@@ -0,0 +1,136 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config PREEMPT_NONE_BUILD
+	bool
+
+config PREEMPT_VOLUNTARY_BUILD
+	bool
+
+config PREEMPT_BUILD
+	bool
+	select PREEMPTION
+	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
+
+choice
+	prompt "Preemption Model"
+	default PREEMPT_NONE
+
+config PREEMPT_NONE
+	bool "No Forced Preemption (Server)"
+	select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC
+	help
+	  This is the traditional Linux preemption model, geared towards
+	  throughput. It will still provide good latencies most of the
+	  time, but there are no guarantees and occasional longer delays
+	  are possible.
+
+	  Select this option if you are building a kernel for a server or
+	  scientific/computation system, or if you want to maximize the
+	  raw processing power of the kernel, irrespective of scheduling
+	  latencies.
+
+config PREEMPT_VOLUNTARY
+	bool "Voluntary Kernel Preemption (Desktop)"
+	depends on !ARCH_NO_PREEMPT
+	select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC
+	help
+	  This option reduces the latency of the kernel by adding more
+	  "explicit preemption points" to the kernel code. These new
+	  preemption points have been selected to reduce the maximum
+	  latency of rescheduling, providing faster application reactions,
+	  at the cost of slightly lower throughput.
+
+	  This allows reaction to interactive events by allowing a
+	  low priority process to voluntarily preempt itself even if it
+	  is in kernel mode executing a system call. This allows
+	  applications to run more 'smoothly' even when the system is
+	  under load.
+
+	  Select this if you are building a kernel for a desktop system.
+
+config PREEMPT
+	bool "Preemptible Kernel (Low-Latency Desktop)"
+	depends on !ARCH_NO_PREEMPT
+	select PREEMPT_BUILD
+	help
+	  This option reduces the latency of the kernel by making
+	  all kernel code (that is not executing in a critical section)
+	  preemptible.  This allows reaction to interactive events by
+	  permitting a low priority process to be preempted involuntarily
+	  even if it is in kernel mode executing a system call and would
+	  otherwise not be about to reach a natural preemption point.
+	  This allows applications to run more 'smoothly' even when the
+	  system is under load, at the cost of slightly lower throughput
+	  and a slight runtime overhead to kernel code.
+
+	  Select this if you are building a kernel for a desktop or
+	  embedded system with latency requirements in the milliseconds
+	  range.
+
+config PREEMPT_RT
+	bool "Fully Preemptible Kernel (Real-Time)"
+	depends on EXPERT && ARCH_SUPPORTS_RT
+	select PREEMPTION
+	help
+	  This option turns the kernel into a real-time kernel by replacing
+	  various locking primitives (spinlocks, rwlocks, etc.) with
+	  preemptible priority-inheritance aware variants, enforcing
+	  interrupt threading and introducing mechanisms to break up long
+	  non-preemptible sections. This makes the kernel, except for very
+	  low level and critical code paths (entry code, scheduler, low
+	  level interrupt handling) fully preemptible and brings most
+	  execution contexts under scheduler control.
+
+	  Select this if you are building a kernel for systems which
+	  require real-time guarantees.
+
+endchoice
+
+config PREEMPT_COUNT
+       bool
+
+config PREEMPTION
+       bool
+       select PREEMPT_COUNT
+
+config PREEMPT_DYNAMIC
+	bool "Preemption behaviour defined on boot"
+	depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT
+	select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY
+	select PREEMPT_BUILD
+	default y if HAVE_PREEMPT_DYNAMIC_CALL
+	help
+	  This option allows to define the preemption model on the kernel
+	  command line parameter and thus override the default preemption
+	  model defined during compile time.
+
+	  The feature is primarily interesting for Linux distributions which
+	  provide a pre-built kernel binary to reduce the number of kernel
+	  flavors they offer while still offering different usecases.
+
+	  The runtime overhead is negligible with HAVE_STATIC_CALL_INLINE enabled
+	  but if runtime patching is not available for the specific architecture
+	  then the potential overhead should be considered.
+
+	  Interesting if you want the same pre-built kernel should be used for
+	  both Server and Desktop workloads.
+
+config SCHED_CORE
+	bool "Core Scheduling for SMT"
+	depends on SCHED_SMT
+	help
+	  This option permits Core Scheduling, a means of coordinated task
+	  selection across SMT siblings. When enabled -- see
+	  prctl(PR_SCHED_CORE) -- task selection ensures that all SMT siblings
+	  will execute a task from the same 'core group', forcing idle when no
+	  matching task is found.
+
+	  Use of this feature includes:
+	   - mitigation of some (not all) SMT side channels;
+	   - limiting SMT interference to improve determinism and/or performance.
+
+	  SCHED_CORE is default disabled. When it is enabled and unused,
+	  which is the likely usage by Linux distributions, there should
+	  be no measurable impact on performance.
+
+