02-01-2018
There is nothing "dead" about BSD. BSD lives in the heart and soul of MacOS, and MacOS is a very popular computer operating system. All software changes over time, and BSD is no exception and BSD changed the heart of the MacOS forever:
Reference:
BSD Overview
Quote:
BSD Overview
The BSD portion of the OS X kernel is derived primarily from FreeBSD, a version of 4.4BSD that offers advanced networking, performance, security, and compatibility features. BSD variants in general are derived (sometimes indirectly) from 4.4BSD-Lite Release 2 from the Computer Systems Research Group (CSRG) at the University of California at Berkeley. BSD provides many advanced features, including the following:
Preemptive multitasking with dynamic priority adjustment. Smooth and fair sharing of the computer between applications and users is ensured, even under the heaviest of loads.
Multiuser access. Many people can use an OS X system simultaneously for a variety of things. This means, for example, that system peripherals such as printers and disk drives are properly shared between all users on the system or the network and that individual resource limits can be placed on users or groups of users, protecting critical system resources from overuse.
Strong TCP/IP networking with support for industry standards such as SLIP, PPP, and NFS. OS X can interoperate easily with other systems as well as act as an enterprise server, providing vital functions such as NFS (remote file access) and email services, or Internet services such as HTTP, FTP, routing, and firewall (security) services.
Memory protection. Applications cannot interfere with each other. One application crashing does not affect others in any way.
Virtual memory and dynamic memory allocation. Applications with large appetites for memory are satisfied while still maintaining interactive response to users. With the virtual memory system in OS X, each application has access to its own 4 GB memory address space; this should satisfy even the most memory-hungry applications.
Support for kernel threads based on Mach threads. User-level threading packages are implemented on top of kernel threads. Each kernel thread is an independently scheduled entity. When a thread from a user process blocks in a system call, other threads from the same process can continue to execute on that or other processors. By default, a process in the conventional sense has one thread, the main thread. A user process can use the POSIX thread API to create other user threads.
SMP support. Support is included for computers with multiple CPUs.
Source code. Developers gain the greatest degree of control over the BSD programming environment because source is included.
Many of the POSIX APIs.
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LEARN ABOUT FREEBSD
sched_4bsd
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