2015-08-27 21:53:54 +08:00
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.. _microkernel_fibers:
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Fiber Services
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##############
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Concepts
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********
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A fiber is a lightweight, non-preemptible thread of execution that implements
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a portion of an application's processing. It is is normally used when writing
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device drivers and other performance critical work.
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A microkernel application can use all of the fiber capabilities that are
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available to a nanokernel application; for more information see
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:ref:`Nanokernel Fiber Services <nanokernel_fibers>`.
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While a fiber often uses one or more nanokernel object types to carry
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out its work, it can also interact with microkernel events and semaphores
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to a limited degree. For example, a fiber can signal a task by giving a
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microkernel semaphore, but it cannot take a microkernel semaphore. For more
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information see :ref:`microkernel_events` and :ref:`microkernel_semaphores`.
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2015-09-01 00:57:39 +08:00
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.. _microkernel_server_fiber:
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Microkernel Server Fiber
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========================
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The microkernel automatically spawns a system thread, known as the
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*microkernel server* fiber, which performs most operations involving
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microkernel objects; see :ref:`Microkernel Server <microkernel_server>`.
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Both the fiber's stack size and scheduling priority can be configured,
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using the :option:`MICROKERNEL_SERVER_STACK_SIZE` and
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:option:`MICROKERNEL_SERVER_PRIORITY` configuration options, respectively.
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By default, the microkernel server has priority 0 (i.e. highest priority).
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However, this can be changed so that the nanokernel scheduler gives precedence
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to other fibers, such as time-sensitive device driver or application fibers.
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