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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 920
SEC. 11.3
SYSTEM STRUCTURE
889
drivers that can be moved into user-mode processes, where a bug will only trigger
the failure of a single driver (rather than bringing down the entire system), the bet-
ter.
The trend of moving code from the kernel to user-mode processes is expected
to accelerate in the coming years.
The I/O manager also includes the plug-and-play and device power-man-
agement facilities.
Plug-and-play
comes into action when new devices are detect-
ed on the system.
The plug-and-play subcomponent is first notified. It works with
a service, the user-mode plug-and-play manager, to find the appropriate device
driver and load it into the system.
Getting the right one is not always easy and
sometimes depends on sophisticated matching of the specific hardware device ver-
sion to a particular version of the drivers. Sometimes a single device supports a
standard interface which is supported by multiple different drivers, written by dif-
ferent companies.
We will study I/O further in Sec. 11.7 and the most important NT file system,
NTFS, in Sec. 11.8.
Device power management reduces power consumption when possible, ex-
tending battery life on notebooks, and saving energy on desktops and servers. Get-
ting power management correct can be challenging, as there are many subtle
dependencies between devices and the buses that connect them to the CPU and
memory.
Power consumption is not affected just by what devices are powered-on,
but also by the clock rate of the CPU, which is also controlled by the device power
manager.
We will take a more in depth look at power management in Sec. 11.9.
The
process manager
manages the creation and termination of processes and
threads, including establishing the policies and parameters which govern them.
But the operational aspects of threads are determined by the kernel layer, which
controls scheduling and synchronization of threads, as well as their interaction
with the control objects, like APCs. Processes contain threads, an address space,
and a handle table containing the handles the process can use to refer to kernel-
mode objects.
Processes also include information needed by the scheduler for
switching between address spaces and managing process-specific hardware infor-
mation (such as segment descriptors).
We will study process and thread man-
agement in Sec. 11.4.
The executive
memory manager
implements the demand-paged virtual mem-
ory architecture.
It manages the mapping of virtual pages onto physical page
frames, the management of the available physical frames, and management of the
pagefile on disk used to back private instances of virtual pages that are no longer
loaded in memory.
The memory manager also provides special facilities for large
server applications such as databases and programming language run-time compo-
nents such as garbage collectors.
We will study memory management later in this
chapter, in Sec. 11.5.
The
cache manager
optimizes the performance of I/O to the file system by
maintaining a cache of file-system pages in the kernel virtual address space.
The
cache manager uses virtually addressed caching, that is, organizing cached pages
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