Introduction to RTEMS - Challenge VxWorks RTOS RTEMS, A Rivail of vxWorks
Source www.rtems.net author ray@rtems.net
RTEMS is the first embedded system developed by the US military. The earliest use of the US defense system, the early name is the real-time missive for miss systems, and later renamed the real-time military system (Real Time Executive for Military Systems), The current full name is in real time, and his feature is very stable and the speed is fast. It is now an open source project RTOS, there is still a lot of users around the world, including Motorola, Lucent, etc. He has the following characteristics:
Very good real-time performance (formerly controlled missile, then worse, there is no difference) Extremely stably contains the POSIX 1003.1B API, and supports POSIX Thread provides PSOS API, and the project on PSOS can easily ported to RTEMS. Following ITron's API system scalable (also often said scalable) multitasking, supporting event driver, priority scheduling, preemptive schedule Synchronization and communication optimization based on statistical monotonic frequency RMS scheduling (RATE MONOTONIC) Scheduling) Priority Height Protocols PCP (Priority CEILING Protocols) Supports priority inheritance for solving priority reversal, support multiprocessor architecture (not only supporting the same processor, also supports heterogeneous processors such as ARM DSP) ) Responsible interrupt management height configurability provides reusable ANSI C library Note: TRON full name is (ITRON (ITRON), ITron (Industrial Tron) is a protocol led by many famous IT companies Develop organizations while IRTON also represents a standard for real-time embedded systems. ITron proposes a series of specifications for real-time operating systems (including system call interface specifications, task scheduling interface specifications, TCP / IP network link API specifications, local and remote debug interface specifications, etc.), follow this standardized operating system upper software Mutual transplantation is a bit similar to POSIX in the UNIX world. All large IT companies in Japan have developed their own ITron-based embedded systems. He also provides a lot of additional properties:
Excellent network support, support BSD sets, TCP / IP, UDP / IP, TFTP, FTPD, HTTPD, SNMP, NTP, ICMP, ARP, DNS Client, PPP, Remote Console, SNMP support graphical interface: MicroWindows GUI support WebServer (Goahead) supports Corba (Omniorb) to support a large number of OpenSource libraries, such as TCL, Readline, Zlib, NCurses, Libavl to provide C support for most APIs (optional) Support ADA Support file system current RTEMS is an open source project of GPL ( Accurately, it is a variant of GPL), widely used in military, industrial, scientific research and other fields. Many professional software (compared, such as EPICs) began to be transplanted on the RTEMS platform. RTEMS provides a reliable real-time core for less memory and less CPU-frequency embedded systems for less memory. The system is divided into several modules, and the user can take the need to cut according to the actual application. The following test has been tested in the international control annual meeting, the hardware platform of the test is PowerPC 604 (300MHz), RTLinux, RTEMS, and VXWORKS BSPs are provided by Motorola, including initialization, interrupt processing, ordinary program (Including network programs, SPI, serial port, etc.). 2,000,000 interrupts were generated in the test, and the average frequency of the interrupt was 4 kHz. It can be seen that this test program is a strict test for the real-time and task scheduling of the kernel. The results of the test are shown in the following table: (unit 10-6s) interrupt delay
Context conversion
System load is medium
maximum
average
maximum
average
RTLinux
13.5
1.7
33.1
8.7
RTEMS1
14.9
1.3
16.9
2.3
RTEMS
15.1
1.3
16.4
2.2
Vxworks
13.1
2.0
19.0
3.1
Heavy load
RTLinux
196.8
2.1
193.9
11.2
RTEMS1
19.2
2.4
213
10.4
RTEMS
20.5
2.9
51.3
3.7
Vxworks
25.2
2.9
38.8
9.5
Note: RTEMS1 (using the PTHREAD library) It can be seen from the results that RTLinux is far less than VxWorks, whether it is real-time or thread task. Especially in the case of heavy load, the delay fluctuation of the interruption is very powerful. Imagine, RTLinux His interrupt processing average time is 2.1US but it may be handled in 200 su actual application. This cannot be allowed in the system where there is a strict requirements. At the same time, it can be seen that RTEMS is ideal for performance indicators of testing, basically reaching or exceeding the old business system VxWorks. It is worth mentioning that RTEMS has declined after using the PTHREAD library. But the worst case is not poor than RTLinux. But people are delightful, the performance of the PTHread library has already improved a lot, and the details can be referred to the list of mails in RTEMS. Since I called the old brother in the embedded system, it supported the CPU type naturally, it can be said that as long as it is supported by GCC, RTEMS can support. One is worth mentioning is the CPU
