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sched_ule(4) [freebsd man page]

SCHED_ULE(4)						   BSD Kernel Interfaces Manual 					      SCHED_ULE(4)

sched_ule -- ULE scheduler SYNOPSIS
The sched_ule scheduler provides a number of advanced scheduler features not present in sched_4bsd(4), the traditional system scheduler. These features address SMP and interactivity and include: o Thread CPU affinity. o CPU topology awareness, including for hyper-threading. o Per-CPU run queues. o Interactivity heuristics that detect interactive applications and schedules them preferentially under high load. The following sysctls are relevant to the operation of sched_ule: 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. SEE ALSO
sched_4bsd(4), sysctl(8) HISTORY
The sched_ule scheduler first appeared in FreeBSD 5.1. AUTHORS
Jeff Roberson <> BSD
August 10, 2012 BSD

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SCHED_4BSD(9)						   BSD Kernel Developer's Manual					     SCHED_4BSD(9)

sched_4bsd -- The 4.4BSD thread scheduler SYNOPSIS
#include <sys/sched.h> void resetpriority(lwp_t *l); void sched_tick(struct cpu_info *ci); void sched_schedclock(lwp_t *l); void sched_pstats_hook(struct proc *p, int minslp); void sched_setrunnable(lwp_t *l); void updatepri(lwp_t *l); DESCRIPTION
The traditional 4.4BSD scheduler employs a ``multilevel feedback queues'' algorithm, favouring interactive, short-running threads to CPU- bound ones. resetpriority() recomputes the priority of a thread running in user mode. If the resulting priority is higher than that of the current thread, a reschedule is arranged. sched_tick() gets called from hardclock(9) every 100ms to force a switch between equal priority threads. The priority of the current thread is adjusted through sched_schedclock(). The priority of a thread gets worse as it accumulates CPU time. sched_pstats_hook() gets called from sched_pstats() every Hz ticks in order to recompute the priorities of all threads. sched_setrunnable() checks if an LWP has slept for more than one second. If so, its priority is updated by updatepri(). CODE REFERENCES
The 4.4BSD scheduler subsystem is implemented within the file sys/kern/sched_4bsd.c. SEE ALSO
csf(9), hardclock(9), mi_switch(9), sched_m2(9), userret(9) Marshall Kirk McKusick, Keith Bostic, Michael J. Karels, and John S. Quarterman, The Design and Implementation of the 4.4BSD Operating System, Addison Wesley, 1996. BSD
July 14, 2007 BSD
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