Design And Optimization Of Fast Boot Based On Loongson 2K1000B Embedded System

Loongson 2K1000 B is a dual-core processor chip developed by Loongson for network security and mobile intelligent terminals.Under such application scenarios and positioning,the system startup speed is very important.Fast startup is very positive for improving user experience significance.By analyzing the software and hardware system of 2K1000 B,the thesis proposes a specific optimization method for the startup speed of the system and demonstrates the effectiveness of the optimization by experiments.The analysis includes three aspects.Firstly,the boot process of the system is analyzed,including PMON,Linux kernel and system service.Then,different from the traditional method,the ESESC performance evaluation tool is analyzed and adapted to evaluate and analyze the boot time of the kernel on the 2K1000 B processor from the perspective of the number of instructions and clocks.Finally,the overall boot time of the 2K1000 B is measured and analyzed,which focused on the optimizable part of the kernel,including the root file system(FS)mounting,the serial port related process and delay calibration.Through the analysis of the system boot process,the following optimization methods are adopted.First of all,through the pruning,the boot speed of PMON,Linux kernel and system service is improved.Then focus on the Linux kernel part.For the root FS mounting,the waiting delay of the root device is reduced by the Linux Completion and the USB storage device is reduced reasonably.The establishment delay and printing delay of the serial console is optimized by temporarily increase the console printing level.For the delay of serial device initialization,a separate module loading method is used.For the delay calibration process,an optimized method of preset lpj value is used.Finally,according to the analysis of the software framework and the hardware characteristics of 2K1000 B,the CPU hotplug and STD mechanism are adapted,and a fast boot strategy based on STD is established.Through the analysis of the fast boot process,two optimization methods are adopted,including: 1.Maximizing the reclamation of memory to reduce the size of the boot image;2.Reducing the saved process and deleting the user login status so as to avoid the deficiency of the traditional scheme that will retain user information.Through experiments,using the optimization method in this thesis,the boot time of PMON was reduced from17.65 s to 10.75 s,Linux kernel image loading and decompression was reduced from 5.18 s to 3.36 s,Linux kernel initialization was reduced from 17.83 s to 1.38 s,system service initialization is reduced from 18.56 s to 6.51 s.The overall boot time is reduced from 59.22 s to 22.00 s,a decrease of 62.8%.