diff options
authorOliver Schinagl <>2008-05-22 23:49:15 (GMT)
committerOliver Schinagl <>2008-05-22 23:49:15 (GMT)
commit76cc5f76be33d0c8defc2f28b22a117202ad7f6d (patch)
parent78087a859a62ccd0682ab8267bfda8b32bc3aa41 (diff)
introduction, background motiviation and conclusion & discussion added.
2 files changed, 16 insertions, 1 deletions
diff --git a/report/chapter1.tex b/report/chapter1.tex
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--- a/report/chapter1.tex
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@@ -1 +1,13 @@
-\section{Background} \ No newline at end of file
+Our world is getting more and more surrounded by electronical devices. Only a few years ago our surroundings were limited to Radio's and Televisions. Soon after we got our Microwaves and washing machines, not to mention the boom in the mobile phone corner. All these devices require Operating systems and nearly all require real-time operating systems. \\
+To define a real-time operating system is beyond the scope of this article, what is not however is that all (real-time) operating systems use some sort of scheduling algorithm. \\
+We have done a literature study concerining one of these algorithms, called Fixed Priority Deferred Schedule (FPDS) and looked at various aspects of it. \\
+FPPS does many great things. One of which however is not, dealing with caches. Caches are great things if you can use them. Audio/Video almost always work a lot faster with caches, so if you like to use caches in a real-time system, there is a scheduling algorythm that allows exactly this, namly is FPDS. FPDS allows the uses of caches, and still behaves like a real-time system. \\
+Resource control can get complex very fast, due to things like Interupt Service Routines (ISR) and buffers to actually access certain resources. With FPPS this is very complex task and introduces a lot of overhead. One of the design goals of FPDS was to simply this and thus also reducing the overhead. \\
diff --git a/report/chapter5.tex b/report/chapter5.tex
index 033182e..15e5700 100644
--- a/report/chapter5.tex
+++ b/report/chapter5.tex
@@ -1,2 +1,5 @@
\section{Discussion and conclusion}
+If an application requires caches, like Video decoding does, then FPDS is a very interesting option. This because FPDS allows the use of caches, yet allowing the system to act in a real-time manner. This however only, and only if, very occasional misses deadlines are acceptable of high priority tasks, since FPDS allows a lower priority task to block a high priority task. \\
+What however, if there are a lot of cache misses? If this is the case, then you could argue that either, the system was designed wrong, either by using a cache that shouldn't have been used in the first place. Or the cache would not be sufficient. On the other hand, it can be argued that there are several algorithms that prove a system is always scheduable. What these algorithms do not account for when the input data is variable. Like for example a Video-data stream from a satelite. This video data stream is unpredictable and can be out of specification. If this is the case, it may still happen that the scheduler misses it's deadline if the video decoding all of a sudden requires more CPU power. \\