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# scheduler.cdl
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#
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# configuration data related to the kernel schedulers
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#
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# ====================================================================
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#####ECOSGPLCOPYRIGHTBEGIN####
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## -------------------------------------------
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## This file is part of eCos, the Embedded Configurable Operating System.
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## Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
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##
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## eCos is free software; you can redistribute it and/or modify it under
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## the terms of the GNU General Public License as published by the Free
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## Software Foundation; either version 2 or (at your option) any later version.
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##
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## eCos is distributed in the hope that it will be useful, but WITHOUT ANY
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## WARRANTY; without even the implied warranty of MERCHANTABILITY or
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## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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## for more details.
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##
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## You should have received a copy of the GNU General Public License along
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## with eCos; if not, write to the Free Software Foundation, Inc.,
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## 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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##
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## As a special exception, if other files instantiate templates or use macros
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## or inline functions from this file, or you compile this file and link it
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## with other works to produce a work based on this file, this file does not
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## by itself cause the resulting work to be covered by the GNU General Public
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## License. However the source code for this file must still be made available
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## in accordance with section (3) of the GNU General Public License.
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##
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## This exception does not invalidate any other reasons why a work based on
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## this file might be covered by the GNU General Public License.
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##
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## Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
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## at http://sources.redhat.com/ecos/ecos-license/
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## -------------------------------------------
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#####ECOSGPLCOPYRIGHTEND####
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# ====================================================================
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######DESCRIPTIONBEGIN####
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#
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# Author(s): jskov
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# Original data: nickg
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# Contributors:
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# Date: 1999-07-05
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#
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#####DESCRIPTIONEND####
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#
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# ====================================================================
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cdl_interface CYGINT_KERNEL_SCHEDULER {
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display "Number of schedulers in this configuration"
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no_define
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requires 1 == CYGINT_KERNEL_SCHEDULER
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}
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cdl_interface CYGINT_KERNEL_SCHEDULER_UNIQUE_PRIORITIES {
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display "Non-zero if the active schedule only has unique priorities"
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description "
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Not all schedulers allow mutiple threads to use the same
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priority. That property is signalled via this option, allowing
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scheduler and tests to behave accordingly."
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}
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# FIXME: The two below options must be mutually exclusive
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cdl_component CYGSEM_KERNEL_SCHED_MLQUEUE {
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display "Multi-level queue scheduler"
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default_value 1
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implements CYGINT_KERNEL_SCHEDULER
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description "
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The multi-level queue scheduler supports multiple priority
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levels and multiple threads at each priority level.
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Preemption between priority levels is automatic. Timeslicing
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within a given priority level is controlled by a separate
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configuration option."
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cdl_option CYGDBG_KERNEL_TRACE_TIMESLICE {
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display "Output timeslices when tracing"
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active_if CYGDBG_USE_TRACING
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requires !CYGDBG_INFRA_DEBUG_TRACE_ASSERT_SIMPLE
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requires !CYGDBG_INFRA_DEBUG_TRACE_ASSERT_FANCY
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default_value 0
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description "
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When tracing is enabled, output trace messages every
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timeslice. This can be quite verbose so is disabled by
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default."
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}
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}
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cdl_option CYGSEM_KERNEL_SCHED_BITMAP {
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display "Bitmap scheduler"
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default_value 0
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implements CYGINT_KERNEL_SCHEDULER
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implements CYGINT_KERNEL_SCHEDULER_UNIQUE_PRIORITIES
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requires !CYGPKG_KERNEL_SMP_SUPPORT
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description "
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The bitmap scheduler supports multiple priority levels but
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only one thread can exist at each priority level. This means
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that scheduling decisions are very simple and hence the
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scheduler is efficient. Preemption between priority levels is
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automatic. Timeslicing within a given priority level is
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irrelevant since there can be only one thread at each
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priority level."
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}
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#cdl_option CYGSEM_KERNEL_SCHED_LOTTERY {
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# display "Lottery scheduler"
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# type radio
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# description "
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# This scheduler is not yet available."
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#}
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cdl_option CYGPRI_KERNEL_SCHED_IMPL_HXX {
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display "Scheduler header file"
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flavor data
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description "
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This option sets a preprocessor symbol which names the header
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file for the selected scheduler. It is used internally by the
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common scheduler code to include the correct header file."
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calculated { \
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CYGSEM_KERNEL_SCHED_BITMAP ? "" :\
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CYGSEM_KERNEL_SCHED_MLQUEUE ? "" :\
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CYGSEM_KERNEL_SCHED_LOTTERY ? "" :\
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"!!!-- Configuration broken - no scheduler selected --!!!"}
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}
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# NOTE: This option only makes sense if the current scheduler
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# supports multiple priority levels.
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cdl_component CYGNUM_KERNEL_SCHED_PRIORITIES {
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display "Number of priority levels"
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flavor data
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legal_values 1 to 32
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default_value 32
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#active_if CYGINT_KERNEL_SCHED_PRIORITY_SCHEDULER
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description "
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This option controls the number of priority levels that are
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available. For some types of scheduler including the bitmap
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scheduler this may impose an upper bound on the number of
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threads in the system. For other schedulers such as the
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mlqueue scheduler the number of threads is independent from
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the number of priority levels. Note that the lowest priority
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level is normally used only by the idle thread, although
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application threads can run at this priority if necessary."
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cdl_option CYGNUM_KERNEL_SCHED_BITMAP_SIZE {
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display "Bitmap size"
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flavor data
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calculated {"CYGNUM_KERNEL_SCHED_PRIORITIES"}
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description "
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This option automatically defines the size of bitmap
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used to track occupied priority levels."
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}
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cdl_option CYGIMP_KERNEL_SCHED_SORTED_QUEUES {
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display "Dequeue oldest threads first"
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flavor bool
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default_value 0
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description "
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With this option enabled, threads queued in a thread queue
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will be dequeued in priority order, rather than last in,
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first out (LIFO). Threads of equal priority are dequeued
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oldest first. The only exception is the scheduler run
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queues where order is less important as each is already
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sorted by priority. Note that this makes the thread queueing
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less deterministic."
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}
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}
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# ---------------------------------------------------------------------
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# Timeslice options
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# NOTE: this option only makes sense for some of the schedulers.
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# Timeslicing is irrelevant for bitmap schedulers.
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cdl_component CYGSEM_KERNEL_SCHED_TIMESLICE {
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display "Scheduler timeslicing"
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requires !CYGSEM_KERNEL_SCHED_BITMAP
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requires CYGVAR_KERNEL_COUNTERS_CLOCK
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default_value 1
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description "
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Some schedulers including the mlqueue scheduler support
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timeslicing. This means that the kernel will check regularly
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whether or not there is another runnable thread with the
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same priority, and if there is such a thread there will be
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an automatic context switch. Not all applications require
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timeslicing, for example because every thread performs a
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blocking operation regularly. For these applications it is
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possible to disable timeslicing, which reduces the overheads
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associated with timer interrupts."
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cdl_option CYGNUM_KERNEL_SCHED_TIMESLICE_TICKS {
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display "Number of clock ticks between timeslices"
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flavor data
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legal_values 1 to 65535
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default_value 5
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description "
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Assuming timeslicing is enabled, how frequently should it
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take place? The value of this option corresponds to the
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number of clock ticks that should occur before a timeslice
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takes place, so increasing the value reduces the frequency
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of timeslices."
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}
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cdl_option CYGSEM_KERNEL_SCHED_TIMESLICE_ENABLE {
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display "Support runtime enable of timeslice per-thread"
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flavor bool
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default_value false
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description "This option makes timslicing a per-thread runtime
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option. When enabled, threads may have timeslicing
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turned on or off dynamically. This is generally used
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by higher level APIs (such as POSIX) to implement
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differing scheduling policies."
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}
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}
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# ---------------------------------------------------------------------
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# ASR support options
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cdl_component CYGSEM_KERNEL_SCHED_ASR_SUPPORT {
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display "Enable ASR support"
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flavor bool
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default_value false
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description "
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This component controls support for Asynchronous Service
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Routines (ASRs). This is a function that may be called
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from the scheduler when it has just exited the scheduler
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lock. This is primarily for use by API compatibility layers."
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cdl_option CYGSEM_KERNEL_SCHED_ASR_GLOBAL {
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display "Make ASR function global"
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flavor bool
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default_value true
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description "
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This option controls whether the ASR function is shared by
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all threads, or whether each thread may have its own ASR
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function."
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}
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cdl_option CYGSEM_KERNEL_SCHED_ASR_DATA_GLOBAL {
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display "Make ASR data global"
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flavor bool
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default_value true
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description "
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This option controls whether the ASR data is shared by
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all threads, or whether each thread may have its own ASR
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data. This is independent of the previous option because
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it may be useful to pass per-thread data to a shared ASR
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function."
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}
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}
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# EOF scheduler.cdl
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