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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 620
SEC. 8.5
SUMMARY
589
often put on top of the operating system to provide a uniform layer for applications
to interact with. The various kinds include document-based, file-based, ob-
ject-based, and coordination-based middleware. Some examples are the World
Wide Web, CORBA, and Linda.
PROBLEMS
1.
Can the USENET newsgroup system or the SETI@home project be considered distrib-
uted systems?
(SETI@home uses several million idle personal computers to analyze
radio telescope data to search for extraterrestrial intelligence.)
If so, how do they relate
to the categories described in Fig. 8-1?
2.
What happens if three CPUs in a multiprocessor attempt to access exactly the same
word of memory at exactly the same instant?
3.
If a CPU issues one memory request every instruction and the computer runs at 200
MIPS, about how many CPUs will it take to saturate a 400-MHz bus? Assume that a
memory reference requires one bus cycle. Now repeat this problem for a system in
which caching is used and the caches have a 90% hit rate. Finally, what cache hit rate
would be needed to allow 32 CPUs to share the bus without overloading it?
4.
Suppose that the wire between switch 2A and switch 3B in the omega network of
Fig. 8-5 breaks. Who is cut off from whom?
5.
How is signal handling done in the model of Fig. 8-7?
6.
When a system call is made in the model of Fig. 8-8, a problem has to be solved im-
mediately after the trap that does not occur in the model of Fig. 8-7. What is the nature
of this problem and how might it be solved?
7.
Rewrite the
enter
region
code of Fig. 2-22 using the pure read to reduce thrashing
induced by the
TSL
instruction.
8.
Multicore CPUs are beginning to appear in conventional desktop machines and laptop
computers. Desktops with tens or hundreds of cores are not far off. One possible way
to harness this power is to parallelize standard desktop applications such as the word
processor or the web browser. Another possible way to harness the power is to paral-
lelize the services offered by the operating system -- e.g., TCP processing -- and com-
monly-used library services -- e.g., secure http library functions). Which approach ap-
pears the most promising? Why?
9.
Are critical regions on code sections really necessary in an SMP operating system to
avoid race conditions or will mutexes on data structures do the job as well?
10.
When the
TSL
instruction is used for multiprocessor synchronization, the cache block
containing the mutex will get shuttled back and forth between the CPU holding the
lock and the CPU requesting it if both of them keep touching the block.
To reduce bus
traffic, the requesting CPU executes one
TSL
every 50 bus cycles, but the CPU holding
the lock always touches the cache block between
TSL
instructions. If a cache block
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