19b99e9b9SRobert Watson.\" Copyright (c) 2005 Robert N. M. Watson 29b99e9b9SRobert Watson.\" All rights reserved. 39b99e9b9SRobert Watson.\" 49b99e9b9SRobert Watson.\" Redistribution and use in source and binary forms, with or without 59b99e9b9SRobert Watson.\" modification, are permitted provided that the following conditions 69b99e9b9SRobert Watson.\" are met: 79b99e9b9SRobert Watson.\" 1. Redistributions of source code must retain the above copyright 89b99e9b9SRobert Watson.\" notice, this list of conditions and the following disclaimer. 99b99e9b9SRobert Watson.\" 2. Redistributions in binary form must reproduce the above copyright 109b99e9b9SRobert Watson.\" notice, this list of conditions and the following disclaimer in the 119b99e9b9SRobert Watson.\" documentation and/or other materials provided with the distribution. 129b99e9b9SRobert Watson.\" 139b99e9b9SRobert Watson.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 149b99e9b9SRobert Watson.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 159b99e9b9SRobert Watson.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 169b99e9b9SRobert Watson.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 179b99e9b9SRobert Watson.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 189b99e9b9SRobert Watson.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 199b99e9b9SRobert Watson.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 209b99e9b9SRobert Watson.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 219b99e9b9SRobert Watson.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 229b99e9b9SRobert Watson.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 239b99e9b9SRobert Watson.\" SUCH DAMAGE. 249b99e9b9SRobert Watson.\" 259b99e9b9SRobert Watson.\" $FreeBSD$ 269b99e9b9SRobert Watson.\" 279b99e9b9SRobert Watson.Dd April 7, 2005 289b99e9b9SRobert Watson.Os 299b99e9b9SRobert Watson.Dt SCHED_4BSD 4 309b99e9b9SRobert Watson.Sh NAME 319b99e9b9SRobert Watson.Nm sched_4bsd 329b99e9b9SRobert Watson.Nd 4.4BSD Scheduler 339b99e9b9SRobert Watson.Sh SYNOPSIS 349b99e9b9SRobert Watson.Cd "options SCHED_4BSD" 359b99e9b9SRobert Watson.Sh DESCRIPTION 369b99e9b9SRobert Watson.Nm 379b99e9b9SRobert Watsonis the default system scheduler, providing both high throughput and solid 389b99e9b9SRobert Watsoninteractive response in the presence of load. 399b99e9b9SRobert Watson.Pp 409b99e9b9SRobert WatsonThe following sysctls are relevant to the operation of 419b99e9b9SRobert Watson.Nm : 429b99e9b9SRobert Watson.Bl -tag -width indent 439b99e9b9SRobert Watson.It kern.sched.name 449b99e9b9SRobert WatsonThis read-only sysctl reports the name of the active scheduler. 459b99e9b9SRobert Watson.It kern.sched.quantum 469b99e9b9SRobert WatsonThis read-write sysctl reports or sets the length of the quantum (in 479b99e9b9SRobert Watsonmicro-seconds) granted to a thread. 489b99e9b9SRobert Watson.It kern.sched.ipiwakeup.enabled 499b99e9b9SRobert WatsonThis read-write sysctl sets whether or not the scheduler will generate an 509b99e9b9SRobert Watsoninter-processor interrupt (IPI) to an idle CPU when a thread is woken up. 519b99e9b9SRobert WatsonOtherwise, idle CPUs will wait until the next clock tick before looking for 529b99e9b9SRobert Watsonnew work. 539b99e9b9SRobert Watson.It kern.sched.preemption 549b99e9b9SRobert WatsonThis read-only sysctl reports whether or not the kernel is configured to 559b99e9b9SRobert Watsonsupport preemption, which reduces the latency to run lower priority threads 569b99e9b9SRobert Watsonon wakeup. 579b99e9b9SRobert Watson.El 589b99e9b9SRobert Watson.Pp 599b99e9b9SRobert WatsonSome sysctls will be available only on systems supporting SMP. 609b99e9b9SRobert Watson.Sh SEE ALSO 619b99e9b9SRobert Watson.Xr sched_ule 4 , 629b99e9b9SRobert Watson.Xr sysctl 8 639b99e9b9SRobert Watson.Sh HISTORY 649b99e9b9SRobert WatsonThe 659b99e9b9SRobert Watson.Nm 669b99e9b9SRobert Watsonscheduler has been present, in various forms, since the inception of 679b99e9b9SRobert Watson.Bx . 689b99e9b9SRobert Watson.Sh BUGS 699b99e9b9SRobert WatsonWhile a highly robust and time-tested scheduler, 709b99e9b9SRobert Watson.Nm 719b99e9b9SRobert Watsonlacks specific knowledge of how to schedule advantageously in non-symetric 729b99e9b9SRobert Watsonprocessor configurations, such as hyper-threading. 73