started section operating system needs

git-svn-id: svn+ssh://mecka.net/home/svn/rtcorba-paper@9 da047780-0f9f-48de-953f-cd541ee48bbd

1 files changed, 6 insertions, 11 deletions

diff --git a/paper.tex b/paper.tex
index 9cda653..08fa6f6 100755
--- a/paper.tex
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@@ -165,17 +165,6 @@ To simulate the transmission of bigger process data images, the parameter \texti
 

 \epsin{sequenzV1}{80}{fig1:f5}{RPC measurement: sequence diagramm}

 

-For testing the priorization based scheduling, the following interface was added:

-

-\begin{lstlisting}

-  interface Data{

-    void Send(in string data);

-  };

-\end{lstlisting}

-

-Each time \textit{Send} was called, the Receiver did a calculation of faculty(100). The \textit{Data} interface was hosted with lower priority, then the Put interface.

-

-

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@@ -192,6 +181,12 @@ As soon as the value of the digital input of the Supplier changes, the new value
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 \section{Needed operating system functionalities}

 

+An TAO ORB can only schedule its CORBA requests correctly, if the underlying operating system has an priorization based scheduler, with a defined maximum scheduling latency. The timer and scheduling latency of a linux system can be determined with cyclictest. For example, the worst case latency on a RT\_PREEMPT enabled box is $26 \mu s$. The same test, on the same box, but with RT\_PREEMPT disabled is $39.6 ms$.

+

+The operating system should support priorization of device i/o data. The real-time application must not beeing interrupted by incomming traffic on any device, excepted data the real-time application must react on (e.g. digital inputs). On a RT\_PREEMPT enabled linux, the most part of all ISR\footnote{interrupt service routine}s are done in kernel threads, which can be priorized from userspace. This solution has two little cons: IRQ sharing and the softirqs for networking. IRQ sharing prevents from a real per device priorization. The softirqs for networking handle the traffic of all NICs in the system. So the priorization of network data from a specific device is not possible. But in case real-time networking gets more and more important, the community works on a solution for this issue.

+

+real-time capable network drivers

+

 

 \section{Conclusion}