SCHED_4BSD(4) BSD Kernel Interfaces Manual SCHED_4BSD(4)
sched_4bsd -- 4.4BSD Scheduler
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:
This read-only sysctl reports the name of the active scheduler.
This read-write sysctl reports or sets the length of the quantum
(in micro-seconds) granted to a thread.
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.
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.
The sched_4bsd scheduler has been present, in various forms, since the
inception of BSD.
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