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SCHED_4BSD(4)            BSD Kernel Interfaces Manual            SCHED_4BSD(4)

NAME
     sched_4bsd -- 4.4BSD Scheduler

SYNOPSIS
     options SCHED_4BSD

DESCRIPTION
     sched_4bsd is the default system scheduler, providing both high through-
     put and solid interactive response in the presence of load.

     The following sysctls are relevant to the operation of sched_4bsd:

     kern.sched.name
             This read-only sysctl reports the name of the active scheduler.

     kern.sched.quantum
             This read-write sysctl reports or sets the length of the quantum
             (in micro-seconds) granted to a thread.

     kern.sched.ipiwakeup.enabled
             This read-write sysctl sets whether or not the scheduler will
             generate an inter-processor interrupt (IPI) to an idle CPU when a
             thread is woken up.  Otherwise, idle CPUs will wait until the
             next clock tick before looking for new work.

     kern.sched.preemption
             This read-only sysctl reports whether or not the kernel is con-
             figured to support preemption, which reduces the latency to run
             lower priority threads on wakeup.

     Some sysctls will be available only on systems supporting SMP.

SEE ALSO
     sched_ule(4), sysctl(8)

HISTORY
     The sched_4bsd scheduler has been present, in various forms, since the
     inception of BSD.

BUGS
     While a highly robust and time-tested scheduler, sched_4bsd lacks spe-
     cific knowledge of how to schedule advantageously in non-symmetric pro-
     cessor configurations, such as hyper-threading.

BSD                              April 7, 2005                             BSD