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# ====================================================================

#

#      scheduler.cdl

#

#      configuration data related to the kernel schedulers

#

# ====================================================================

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# ====================================================================

######DESCRIPTIONBEGIN####

#

# Author(s):      jskov

# Original data:  nickg

# Contributors:

# Date:           1999-07-05

#

#####DESCRIPTIONEND####

#

# ====================================================================

cdl_interface CYGINT_KERNEL_SCHEDULER {

    display  "Number of schedulers in this configuration"

    no_define

    requires 1 == CYGINT_KERNEL_SCHEDULER

}

cdl_interface CYGINT_KERNEL_SCHEDULER_UNIQUE_PRIORITIES {

    display  "Non-zero if the active schedule only has unique priorities"

    description "

        Not all schedulers allow mutiple threads to use the same

        priority. That property is signalled via this option, allowing

        scheduler and tests to behave accordingly."

}

# FIXME: The two below options must be mutually exclusive

cdl_component CYGSEM_KERNEL_SCHED_MLQUEUE {

    display       "Multi-level queue scheduler"

    default_value 1

    implements    CYGINT_KERNEL_SCHEDULER

    description   "

        The multi-level queue scheduler supports multiple priority

        levels and multiple threads at each priority level.

        Preemption between priority levels is automatic. Timeslicing

        within a given priority level is controlled by a separate

        configuration option."

    cdl_option CYGDBG_KERNEL_TRACE_TIMESLICE {

        display       "Output timeslices when tracing"

        active_if     CYGDBG_USE_TRACING

        requires      !CYGDBG_INFRA_DEBUG_TRACE_ASSERT_SIMPLE

        requires      !CYGDBG_INFRA_DEBUG_TRACE_ASSERT_FANCY

        default_value 0

        description   "

                When tracing is enabled, output trace messages every

                timeslice. This can be quite verbose so is disabled by

                default."

    }

}

cdl_option CYGSEM_KERNEL_SCHED_BITMAP {

    display       "Bitmap scheduler"

    default_value 0

    implements    CYGINT_KERNEL_SCHEDULER

    implements    CYGINT_KERNEL_SCHEDULER_UNIQUE_PRIORITIES

    requires      !CYGPKG_KERNEL_SMP_SUPPORT

    description   "

        The bitmap scheduler supports multiple priority levels but

        only one thread can exist at each priority level. This means

        that scheduling decisions are very simple and hence the

        scheduler is efficient. Preemption between priority levels is

        automatic. Timeslicing within a given priority level is

        irrelevant since there can be only one thread at each

        priority level."

}

#cdl_option CYGSEM_KERNEL_SCHED_LOTTERY {

#    display      "Lottery scheduler"

#    type          radio

#    description "

#       This scheduler is not yet available."

#}

cdl_option CYGPRI_KERNEL_SCHED_IMPL_HXX {

    display       "Scheduler header file"

    flavor        data

    description   "

        This option sets a preprocessor symbol which names the header

        file for the selected scheduler.  It is used internally by the

        common scheduler code to include the correct header file."

    calculated { \

               CYGSEM_KERNEL_SCHED_BITMAP  ? ""  :\

               CYGSEM_KERNEL_SCHED_MLQUEUE ? "" :\

               CYGSEM_KERNEL_SCHED_LOTTERY ? "" :\

               "!!!-- Configuration broken - no scheduler selected --!!!"}

}

# NOTE: This option only makes sense if the current scheduler

#       supports multiple priority levels.

cdl_component CYGNUM_KERNEL_SCHED_PRIORITIES {

    display       "Number of priority levels"

    flavor        data

    legal_values  1 to 32

    default_value 32

    #active_if     CYGINT_KERNEL_SCHED_PRIORITY_SCHEDULER

    description "

        This option controls the number of priority levels that are

        available. For some types of scheduler including the bitmap

        scheduler this may impose an upper bound on the number of

        threads in the system. For other schedulers such as the

        mlqueue scheduler the number of threads is independent from

        the number of priority levels. Note that the lowest priority

        level is normally used only by the idle thread, although

        application threads can run at this priority if necessary."

    cdl_option CYGNUM_KERNEL_SCHED_BITMAP_SIZE {

        display       "Bitmap size"

        flavor        data

        calculated    {"CYGNUM_KERNEL_SCHED_PRIORITIES"}

        description   "

                This option automatically defines the size of bitmap

                used to track occupied priority levels."

    }

    cdl_option CYGIMP_KERNEL_SCHED_SORTED_QUEUES {

        display       "Dequeue highest priority threads first"

        flavor        bool

        default_value 0

        description   "

            With this option enabled, threads queued in a thread queue

            will be dequeued in priority order, rather than first in,

            first out (FIFO). Threads of equal priority are dequeued

            oldest first. The only exception is the scheduler run

            queues where order is less important as each is already

            sorted by priority. Note that this makes the thread queueing

            less deterministic."

    }

}

# ---------------------------------------------------------------------

# Timeslice options

# NOTE: this option only makes sense for some of the schedulers.

# Timeslicing is irrelevant for bitmap schedulers.

cdl_component CYGSEM_KERNEL_SCHED_TIMESLICE {

    display       "Scheduler timeslicing"

    requires      !CYGSEM_KERNEL_SCHED_BITMAP

    requires      CYGVAR_KERNEL_COUNTERS_CLOCK

    default_value 1

    description "

        Some schedulers including the mlqueue scheduler support

        timeslicing. This means that the kernel will check regularly

        whether or not there is another runnable thread with the

        same priority, and if there is such a thread there will be

        an automatic context switch. Not all applications require

        timeslicing, for example because every thread performs a

        blocking operation regularly. For these applications it is

        possible to disable timeslicing, which reduces the overheads

        associated with timer interrupts."

    cdl_option CYGNUM_KERNEL_SCHED_TIMESLICE_TICKS {

        display       "Number of clock ticks between timeslices"

        flavor        data

        legal_values  1 to 65535

        default_value 5

        description "

            Assuming timeslicing is enabled, how frequently should it

            take place? The value of this option corresponds to the

            number of clock ticks that should occur before a timeslice

            takes place, so increasing the value reduces the frequency

            of timeslices."

    }

    cdl_option CYGSEM_KERNEL_SCHED_TIMESLICE_ENABLE {

        display       "Support runtime enable of timeslice per-thread"

        flavor        bool

        default_value false

        description "This option makes timslicing a per-thread runtime

                     option. When enabled, threads may have timeslicing

                     turned on or off dynamically. This is generally used

                     by higher level APIs (such as POSIX) to implement

                     differing scheduling policies."

    }

}

# ---------------------------------------------------------------------

# ASR support options

cdl_component CYGSEM_KERNEL_SCHED_ASR_SUPPORT {

    display       "Enable ASR support"

    flavor        bool

    default_value false

    description   "

         This component controls support for Asynchronous Service

         Routines (ASRs). This is a function that may be called

         from the scheduler when it has just exited the scheduler

         lock. This is primarily for use by API compatibility layers."

    cdl_option CYGSEM_KERNEL_SCHED_ASR_GLOBAL {

        display       "Make ASR function global"

        flavor        bool

        default_value true

        description "

             This option controls whether the ASR function is shared by

             all threads, or whether each thread may have its own ASR

             function."

    }

    cdl_option CYGSEM_KERNEL_SCHED_ASR_DATA_GLOBAL {

        display       "Make ASR data global"

        flavor        bool

        default_value true

        description "

             This option controls whether the ASR data is shared by

             all threads, or whether each thread may have its own ASR

             data. This is independent of the previous option because

             it may be useful to pass per-thread data to a shared ASR

             function."

    }

}

# EOF scheduler.cdl