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

NAME

     sched_4bsd -- 4.4BSD scheduler

SYNOPSIS

     options SCHED_4BSD

DESCRIPTION

     The sched_4bsd scheduler is the traditional 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 pro-
     cessor configurations, such as hyper-threading.

BSD
								 January 21, 2008							       BSD