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$FreeBSD$
.Dd January 21, 2008 .Dt SCHED_4BSD 4 .Os .Sh NAME .Nm sched_4bsd .Nd "4.4BSD scheduler" .Sh SYNOPSIS .Cd "options SCHED_4BSD" .Sh DESCRIPTION The .Nm scheduler is the traditional system scheduler, providing both high throughput and solid interactive response in the presence of load.
p The following sysctls are relevant to the operation of .Nm : l -tag -width indent t Va kern.sched.name This read-only sysctl reports the name of the active scheduler. t Va kern.sched.quantum This read-write sysctl reports or sets the length of the quantum (in micro-seconds) granted to a thread. t Va 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. t Va 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. .El
p Some sysctls will be available only on systems supporting SMP. .Sh SEE ALSO .Xr sched_ule 4 , .Xr sysctl 8 .Sh HISTORY The .Nm scheduler has been present, in various forms, since the inception of x . .Sh BUGS While a highly robust and time-tested scheduler, .Nm lacks specific knowledge of how to schedule advantageously in non-symmetric processor configurations, such as hyper-threading.