x15/kern/Kconfig

menu "General setup"

config SMP
	bool "Multiprocessor support"
	default y
	---help---
	  Enable support for machines with multiple processors.

config MAX_CPUS
	int "Maximum number of supported CPUs" if SMP
	range 2 512 if SMP
	default "1" if !SMP
	default "128" if SMP
	---help---
	  Maximum number of supported processors.

config CLOCK_FREQ
	int "Low resolution clock frequency"
	range 100 1000
	default 200
	---help---
	  The low resolution clock frequency determines how often low
	  resolution clocks interrupt processors. These clocks drive
	  the timer system. Low values increase throughput and latencies,
	  whereas high values reduce throughput and latencies.

	  The value must be usable as an integer divisor for 1000, with
	  no remainder.

	  Recommended values are 100 for throughput, 1000 for low
	  latencies, and 200 or 250 for a good balance between throughput
	  and latencies.

choice
	prompt "Mutex implementation"
	default MUTEX_PLAIN
	---help---
	  A mutex is a sleeping synchronization object used throughout the
	  kernel and available to kernel applications. As a result, this
	  option affects all mutex users.

	  If in doubt, choose the plain implementation.

config MUTEX_ADAPTIVE
	bool "Adaptive spinning mutex"
	---help---
	  Adaptive spinning mutex, spinning instead of sleeping if the owner
	  is running, in the hope the critical section is short and the mutex
	  will be unlocked soon, to avoid expensive sleep/wakeup operations.
	  This implementation should improve overall performance at the cost
	  of increased latencies.

config MUTEX_PI
	bool "Mutex with priority inheritance"
	---help---
	  Real-time mutex with priority inheritance. This implementation
	  should improve latencies at the cost of overall performance.

config MUTEX_PLAIN
	bool "Plain mutex"
	---help---
	  Default implementation, immediately sleeping on contention.

endchoice

config RCU_WINDOW_CHECK_INTERVAL
	int "Interval between RCU window checks"
	range 1 100
	default 10
	---help---
	  Time (in milliseconds) between two RCU window checks.

	  The RCU system keeps memory used by read-side critical sections
	  until it is safe to release it, which can only be determined when
	  checking windows. As a result, checking windows more frequently
	  may help lower latencies on synchronous RCU waits, and in turn,
	  the amount of memory pending release, at the cost of increased
	  CPU overhead.

config SHELL
	bool "Embedded shell"
	default n
	---help---
	  Enable the embedded shell.

	  The embedded shell is mostly used for diagnostics.

config THREAD_STACK_GUARD
	bool "Thread stack guard pages"
	---help---
	  Enable the use of guard pages around kernel thread stacks to catch
	  overflows. Note that this feature wastes precious kernel virtual
	  memory and has some overhead during thread creation and destruction.

	  If unsure, disable.

config THREAD_MAX_TSD_KEYS
	int "Maximum number of thread-specific data (TSD) keys"
	default 0
	---help---
	  This option is intended for application code embedded in the kernel
	  which may use TSD. The kernel itself never uses them. A value of 0
	  completely disables TSD support.

	  If unsure, set to 0.

config PERFMON
	def_bool n

config PERFMON_MAX_PMCS
	int "Number of performance monitoring counters"
	default 8
	depends on PERFMON
	---help---
	  Number of performance monitoring counters.

	  This value affects the minimum duration of some critical sections
	  that run with interrupts disabled.

endmenu

menu "Debugging"

config KMEM_DEBUG
	bool "Kernel allocator debugging"
	default n
	---help---
	  Enable the debugging of the kernel allocator.

config KMEM_NO_CPU_LAYER
	bool "Disable the CPU layer of the kernel allocator"
	depends on SMP
	default n
	---help---
	  The kernel allocator is made up of two layers named
	  the CPU and slab layers. the CPU layer is responsible
	  for caching objects locally on a processor to reduce
	  contention and cache misses. When reporting kernel
	  memory usage, the CPU layer is ignored, and objects
	  stored in it are accounted as allocated, which can
	  cause confusion when checking the state of the system.

	  This option disables the CPU layer entirely, so that
	  the report usage stats match the actual allocator
	  state.

	  If unsure, disable (leave the CPU layer enabled).

config INIT_DEBUG
	bool "Initialization debugging"
	default n
	---help---
	  Enable the debugging of initialization operations.

config MUTEX_DEBUG
	bool "Mutex debugging"
	default n
	---help---
	  Enable mutex debugging and instrumentation.

config SPINLOCK_DEBUG
	bool "Spinlock debugging"
	default n
	---help---
	  Enable spinlock ownership tracking.

config SREF_DEBUG
	bool "Scalable reference counter debugging"
	select ASSERT
	default n
	---help---
	  Enable scalable reference counter debugging

endmenu