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Modern Operating Systems by Herbert Bos and Andrew S. Tanenb...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf
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Modern Operating Systems by Herbert Bos and Andrew...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Modern Operating Systems by Herbert...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Page 1053
1022
OPERATING SYSTEM DESIGN
CHAP. 12
C
C
Test
modules
Code
Test
system
(a)
Deploy
Dummy
procedure
1
(b)
Plan
Dummy
procedure
2
Dummy
procedure
3
Main
program
Figure 12-11.
(a) Traditional software design progresses in stages.
(b) Alterna-
tive design produces a working system (that does nothing) starting on day 1.
12.5.4 No Silver Bullet
In addition to
The Mythical Man Month
, Brooks also wrote an influential paper
called ‘‘No Silver Bullet’’ (Brooks, 1987).
In it, he argued that none of the many
nostrums being hawked by various people at the time was going to generate an
order-of-magnitude improvement in software productivity within a decade. Experi-
ence shows that he was right.
Among the silver bullets that were proposed were better high-level languages,
object-oriented programming, artificial intelligence, expert systems, automatic pro-
gramming, graphical programming, program verification, and programming envi-
ronments. Perhaps the next decade will see a silver bullet, but maybe we will have
to settle for gradual, incremental improvements.
12.6 TRENDS IN OPERATING SYSTEM DESIGN
In 1899, the head of the U.S. Patent Office, Charles H. Duell, asked then-Presi-
dent McKinley to abolish the Patent Office (and his job!), because, as he put it:
‘‘Everything that can be invented, has been invented’’(Cerf and Navasky, 1984).
Nevertheless, Thomas Edison showed up on his doorstep within a few years with a
couple of new items, including the electric light, the phonograph, and the movie
projector. The point is that the world is constantly changing and operating systems
must adapt to the new reality all the time. In this section, we mention a few trends
that are relevant for operating system designers today.
To avoid confusion, the
hardware developments
mentioned below are here
already.
What is not here is the operating system software to use them effectively.
Page 1054
SEC. 12.6
TRENDS IN OPERATING SYSTEM DESIGN
1023
Generally, when new hardware arrives, what everyone does is just plop the old
software (Linux, Windows, etc.) down on it and call it a day. In the long run, this is
a bad idea. What we need is innovative software to deal with innovative hardware.
If you are a computer science or engineering student or an ICT professional, your
homework assignment is to think up this software.
12.6.1 Virtualization and the Cloud
Virtualization is an idea whose time has definitely come—again. It first sur-
faced in 1967 with the IBM CP/CMS system, but now it is back in full force on the
x86 platform.
Many computers are now running hypervisors on the bare hardware,
as illustrated in Fig. 12-12. The hypervisor creates a number of virtual machines,
each with its own operating system. This phenomenon was discussed in Chap. 7
and appears to be the wave of the future. Nowadays, many companies are taking
the idea further by virtualizing other resources also. For instance, there is much in-
terest in virtualizing the control of network equipment, even going so far as run-
ning the control of their networks in the cloud also. In addition, vendors and re-
searchers constantly work on making hypervisors better for some notion of better:
smaller, faster, or with provable isolation properties.
Hardware
Hypervisor
Windows
Linux
Linux
Other
OS
Virtual machine
Figure 12-12.
A hypervisor running four virtual machines.
12.6.2 Manycore Chips
There used to be a time that memory was so scarce that a programmer knew
every byte in person and celebrated its birthday. Nowaways, programmers rarely
worry about wasting a few megabytes here and there. For most applications, mem-
ory is no longer a scarce resource. What will happen when cores become equally
plentiful? Phrased differently, as manufacturers are putting more and more cores
on a die, what happens if there are so many that a programmers stops worrying
about wasting a few cores here and there?
Manycore chips are here already, but the operating systems for them do not use
them well. In fact, stock operating systems often do not even scale beyond a few
dozens of cores and developers are constantly struggling to remove all the bottle-
necks that limit scalability.
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