[Nikkei BP Society] The world's largest embedded Linux Suite Publisher US Montavista software company, successfully developed an embedded Linux kernel that enhance response performance by joining a mutex (MUTEX) with priority inheritance. The longest answer time of the ordinary Linux kernel is about 100ms, and the Linux kernel of this development has achieved several tens of μs. The longest answer time of ordinary real-time OS is μs, that is, the response performance has been improved to a level that can be competed with real-time OS. The company's technical vice president Kevin Morgan said confidently: "This is expected to replace real-time OS. There is no Linux that Linux does not meet the needs of use in embedded field."
Most of the current embedded Linux uses a predecessor core that can be switched in the middle of the kernel execution path. After the predetermined kernel, the average value of the response performance can be shortened to 1/10 or less compared to the ordinary Linux kernel without this kernel. However, there is no effect on shortening the longest response time. Therefore, Linux cannot be employed in terms of communication control applications such as response performance.
Replace self-locking with mutual exclusion procedures
The LINUX kernel developed this time, by using a mute exclusion program with priority inheritance, replacing a spin lock used to protect the critical regions in the past, shorten the longest answer time. The mutual exclusive program is a common function of a μITron and other common real-time OS. It is a technique that should be considered by improving Linux response performance. Montavista's Morgan said: "After adding a mute exclusive process with priority inheritance, there is a disadvantage that the programs that judge priority when thread locking will produce overhead. Therefore, a mutually exclusive program has not been used in the past." If it is Rotch, just simply wait for the task, so it is more concise compared to the mutex.
Cancel your phone real-time OS, support multi-core
Montavista's goal is to apply the Linux kernel of this development to a mobile phone. Most of the existing mobile phones are running different OS by baseband processing chips and application processors. Since the baseband processing chip with the base station communication is required to have a short answer time, the past Linux does not meet the requirements. For example, install Linux NEC phones, Linux is currently running on the application processor, and the baseband processing chip runs μitron.
If the Linux kernel that has the priority inheritance function of this development can be run on the application processor, it is possible to hand over the call control processing made in the past by the baseband processing chip to the application processor. In this way, you can cancel the existing real-time OS. Since the OS is only Linux, not only the development efficiency is expected to increase, but the baseband processing chip is saved, "also helps to reduce the production cost of the mobile phone." (Morgan) In addition, due to this development Linux kernel also supports symmetrical processing The architecture (SMP), so if the multi-core application processor can be used, the baseband processing chip can be saved in the case of maintaining the entire processing performance.
Montavista has prepared to attract developers to join the development group in order to continue to improve by public code. Click here to click here. In addition, US Timesys is also the same Linux kernel with the same response performance with the Linux kernel. However, "Not open source, I hope to highlight itself." (Montavista's Morgan) (Reporter: into the vine intelligence)
From:
Nikkei BP
