A Real-time Linux System To Support QoS Called QR-Linux

IP network is changing to the next generation integrated business network which integrates the multimedia, such as audio and video. The network quality of service (QoS) has become to the important issue in the research of network. This paper discusses how to support the QoS of real-time multimedia business with OS viewpoint.In this thesis, a real-time Linux system called QR-Linux, which supports QoS, was designed and implemented by added real-time kernel thread to run the Deferring Work of network receiving interrupt, based on the analysises of process scheduling and Bottom Halves and the network subsystem in Linux 2.6 kernel.The Deferring Work is an important issue which works on Real-time performance in Linux. In QR-Linux, the Deferring Work of network receiving interrupt was performed by work queue in process context, so it is preemptible and sleepable. Scheduling the process of protocol stack obviously is the main way of improving the real-time performance of network in QR-Linux. So the essential idea of QR-Linux is: performing the protocol processing of real-time business and non-real-time business with different real-time kernel threads and using the preemptible of process scheduling provided by Linux kernel 2.6, to guarantee the prior processing of real-time business. Thus, implement the DiffServ and support QoS.QR-Linux was implemented by modify Linux kernel 2.6.11, mainly solved three significant problems: the division of real-time and non-real-time data packets, the implementation of real-time work queue and the use of worker thread of network receiving. Then, the Linux kernel was recompiled and the QR-Linux system was constructed.Finally, in the built test environment, the network throughput and the request/response performance of Linux and QR-Linux was tested respectively, as a comparison, using Netperf which is a test tool of network performance. The result indicates that the performance of processing Real-time network data packet and scalable in QR-Linux is better than that in Linux. This certificates the performance of Real-time in QR-Linux, and can support the QoS of the Real-time multimedia task.The QR-Linux system can be applied as a real-time operating system on embedded network device or network console.