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NAME

     sched_4bsd - 4.4BSD scheduler

SYNOPSIS

     options SCHED_4BSD

DESCRIPTION

     The sched_4bsd scheduler is the default system scheduler, providing both
     high throughput 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
             configured 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
     specific knowledge of how to schedule advantageously in non-symmetric
     processor configurations, such as hyper-threading.