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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 1009
CHAP. 11
Windows uses a facility called Autoboost to temporarily raise the priority of a thread
that holds the resource that is required by a higher-priority thread.
How do you think
this works?
In Windows it is easy to implement a facility where threads running in the kernel can
temporarily attach to the address space of a different process.
Why is this so much
harder to implement in user mode?
Why might it be interesting to do so?
Name two ways to give better response time to the threads in important processes.
Even when there is plenty of free memory available, and the memory manager does not
need to trim working sets, the paging system can still frequently be writing to disk.
Windows swaps the processes for modern applications rather than reducing their work-
ing set and paging them.
Why would this be more efficient? (Hint: It makes much less
of a difference when the disk is an SSD.)
Why does the self-map used to access the physical pages of the page directory and
page tables for a process always occupy the same 8 MB of kernel virtual addresses (on
the x86)?
The x86 can use either 64-bit or 32-bit page table entries.
Windows uses 64-bit PTEs
so the system can access more than 4 GB of memory.
With 32-bit PTEs, the self-map
uses only one PDE in the page directory, and thus occupies only 4 MB of addresses
rather than 8 MB.
Why is this?
If a region of virtual address space is reserved but not committed, do you think a VAD
is created for it?
Defend your answer.
Which of the transitions shown in Fig. 11-34 are policy decisions, as opposed to re-
quired moves forced by system events (e.g., a process exiting and freeing its pages)?
Suppose that a page is shared and in two working sets at once.
If it is evicted from one
of the working sets, where does it go in Fig. 11-34? What happens when it is evicted
from the second working set?
When a process unmaps a clean stack page, it makes the transition (5) in Fig. 11-34.
Where does a dirty stack page go when unmapped?
Why is there no transition to the
modified list when a dirty stack page is unmapped?
Suppose that a dispatcher object representing some type of exclusive lock (like a
mutex) is marked to use a notification event instead of a synchronization event to
announce that the lock has been released.
Why would this be bad?
How much would
the answer depend on lock hold times, the length of quantum, and whether the system
was a multiprocessor?
To support POSIX, the native
API supports duplicating a process in
order to support
is shortly followed by an
most of the time.
One example where this was used historically was in the Berkeley
which would backup disks to magnetic tape.
was used as a way of checkpointing
the dump program so it could be restarted if there was an error with the tape device.

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