217 lines
6.6 KiB
Groff
217 lines
6.6 KiB
Groff
.\" $NetBSD: csf.9,v 1.9 2015/05/25 21:02:37 prlw1 Exp $
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.\"
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.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Daniel Sieger.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd October 27, 2014
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.Dt CSF 9
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.Os
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.Sh NAME
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.Nm CSF
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.Nd The
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.Nx
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common scheduler framework
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.Sh SYNOPSIS
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.In sys/sched.h
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.Ft void
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.Fn sched_rqinit "void"
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.Ft void
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.Fn sched_setup "void"
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.Ft void
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.Fn sched_cpuattach "struct cpu_info *"
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.Ft void
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.Fn sched_tick "struct cpu_info *"
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.Ft void
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.Fn sched_schedclock "lwp_t *"
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.Ft bool
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.Fn sched_curcpu_runnable_p "void"
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.Ft lwp_t *
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.Fn sched_nextlwp "void"
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.Ft void
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.Fn sched_enqueue "lwp_t *" "bool"
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.Ft void
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.Fn sched_dequeue "lwp_t *"
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.Ft void
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.Fn sched_nice "struct proc *" "int"
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.Ft void
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.Fn sched_proc_fork "struct proc *" "struct proc *"
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.Ft void
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.Fn sched_proc_exit "struct proc *" "struct proc *"
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.Ft void
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.Fn sched_lwp_fork "lwp_t *"
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.Ft void
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.Fn sched_lwp_exit "lwp_t *"
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.Ft void
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.Fn sched_setrunnable "lwp_t *"
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.Ft void
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.Fn sched_print_runqueue "void (*pr)(const char *, ...)"
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.Ft void
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.Fn sched_pstats_hook "struct proc *" "int"
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.Ft void
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.Fn sched_pstats "void *arg"
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.Ft pri_t
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.Fn sched_kpri "lwp_t *"
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.Ft void
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.Fn resched_cpu "lwp_t *"
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.Ft void
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.Fn setrunnable
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.Ft void
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.Fn schedclock "lwp_t *"
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.Ft void
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.Fn sched_init "void"
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.Sh DESCRIPTION
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.Nm
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provides a modular and self-contained interface for
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implementing different thread scheduling algorithms.
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The different schedulers can be selected at compile-time.
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Currently, the schedulers available are
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.Xr sched_4bsd 9 ,
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the traditional 4.4BSD thread scheduler, and
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.Xr sched_m2 9
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which implements a SVR4/Solaris like approach.
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.Pp
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The interface is divided into two parts: A set of functions each
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scheduler needs to implement and common functions used by all
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schedulers.
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.Sh Scheduler-specific functions
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The following functions have to be implemented by the individual
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scheduler.
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.Ss Scheduler initialization
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.Bl -tag -width compact
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.It Ft void Fn sched_cpuattach "struct cpu_info *"
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Per-CPU scheduler initialization routine.
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.It Ft void Fn sched_rqinit "void"
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Initialize the scheduler's runqueue data structures.
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.It Ft void Fn sched_setup "void"
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Setup initial scheduling parameters and kick off timeout driven
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events.
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.El
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.Ss Runqueue handling
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Runqueue handling is completely internal to the scheduler.
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Other parts of the kernel should access runqueues only through the
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following functions:
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.Bl -tag -width compact
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.It Ft void Fn sched_enqueue "lwp_t *" "bool"
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Place an LWP within the scheduler's runqueue structures.
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.It Ft void Fn sched_dequeue "lwp_t *"
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Remove an LWP from the scheduler's runqueue structures.
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.It Ft lwp_t * Fn sched_nextlwp "void"
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Return the LWP that should run the CPU next.
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.It Ft bool Fn sched_curcpu_runnable_p "void"
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Indicate if there is a runnable LWP for the current CPU.
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.It Ft void Fn sched_print_runqueue "void (*pr)(const char *, ...)"
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Print runqueues in DDB.
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.El
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.Ss Core scheduler functions
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.Bl -tag -width compact
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.It Ft void Fn sched_tick "struct cpu_info *"
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Periodically called from
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.Xr hardclock 9 .
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Determines if a reschedule is necessary, if the running LWP has
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used up its quantum.
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.It Ft void Fn sched_schedclock "lwp_t *"
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Periodically called from
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.Fn schedclock
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in order to handle priority adjustment.
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.El
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.Ss Priority adjustment
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.Bl -tag -width compact
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.It Ft void Fn sched_nice "struct proc *" "int"
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Recalculate the process priority according to its nice value.
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.El
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.Ss General helper functions
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.Bl -tag -width compact
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.It Ft void Fn sched_proc_fork "struct proc *" "struct proc *"
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Inherit the scheduling history of the parent process after
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.Fn fork .
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.It Ft void Fn sched_proc_exit "struct proc *" "struct proc *"
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Charge back a processes parent for its resource usage.
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.It Ft void Fn sched_lwp_fork "lwp_t *"
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LWP-specific version of the above
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.It Ft void Fn sched_lwp_exit "lwp_t *"
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LWP-specific version of the above
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.It Ft void Fn sched_setrunnable "lwp_t *"
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Scheduler-specific actions for
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.Fn setrunnable .
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.It Ft void Fn sched_pstats_hook "struct proc *" "int"
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Scheduler-specific actions for
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.Fn sched_pstats .
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.El
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.Sh Common scheduler functions
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.Bl -tag -width compact
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.It Ft pri_t Fn sched_kpri "lwp_t *"
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Scale a priority level to a kernel priority level, usually for an LWP
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that is about to sleep.
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.It Ft void Fn sched_pstats "void *"
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Update process statistics and check CPU resource allocation.
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.It Ft inline void Fn resched_cpu "lwp_t *"
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Arrange for a reschedule.
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.It Ft void Fn setrunnable "lwp_t *"
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Change process state to be runnable, placing it on a runqueue if it
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is in memory, awakening the swapper otherwise.
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.It Ft void Fn schedclock "lwp_t *"
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Scheduler clock.
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Periodically called from
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.Fn statclock .
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.It Ft void Fn sched_init "void"
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Initialize callout for
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.Fn sched_pstats
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and call
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.Fn sched_setup
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to initialize any other scheduler-specific data.
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.El
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.Sh CODE REFERENCES
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The
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.Nm
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programming interface is defined within the file
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.Pa sys/sys/sched.h .
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.Pp
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Functions common to all scheduler implementations are in
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.Pa sys/kern/kern_synch.c .
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.Pp
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The traditional 4.4BSD scheduler is implemented in
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.Pa sys/kern/sched_4bsd.c .
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.Pp
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The M2 scheduler is implemented in
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.Pa sys/kern/sched_m2.c .
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.Sh SEE ALSO
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.Xr mi_switch 9 ,
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.Xr preempt 9 ,
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.Xr sched_4bsd 9 ,
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.Xr sched_m2 9
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.Sh HISTORY
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The
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.Nm
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appeared in
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.Nx 5.0 .
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.Sh AUTHORS
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The
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.Nm
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was written by
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.An Daniel Sieger
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.Aq dsieger@NetBSD.org .
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