【arm】big-LITTLE architecture and How to check core, frequency, features of CPU and memory infos

Date: 2018.9.3

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1、参考

http://support.hkvstar.com/file/Hi3519_Datasheet.pdf
http://www.hisilicon.com/-/media/Hisilicon/pdf/Surveillance_mobilecam/Hi3519V101.pdf
https://www.silicondevice.com/file.upload/images/Gid1319Pdf_Hi3559_V100_2K4K_MobileCamera_SoC_Brief_Data_Sheet.pdf

2、big-LITTLE architecture

https://en.wikipedia.org/wiki/ARM_big.LITTLE

ARM big.LITTLE is a heterogeneous computing architecture developed by ARM Holdings, coupling relatively battery-saving and slower processor cores (LITTLE) with relatively more powerful and power-hungry ones (big). Typically, only one “side” or the other will be active at once, but since all the cores have access to the same memory regions, workloads can be swapped between Big and Little cores on the fly.[1] The intention is to create a multi-core processor that can adjust better to dynamic computing needs and use less power than clock scaling alone. ARM’s marketing material promises up to a 75% savings in power usage for some activities.[2]

In October 2011, big.LITTLE was announced along with the Cortex-A7, which was designed to be architecturally compatible with the Cortex-A15.[3] In October 2012 ARM announced the Cortex-A53 and Cortex-A57 (ARMv8-A) cores, which are also compatible with each other to allow their use in a big.LITTLE chip.[4] ARM later announced the Cortex-A12 at Computex 2013 followed by the Cortex-A17 in February 2014, both can also be paired in a big.LITTLE configuration with the Cortex-A7.[5][6]

如参考文档中的不同Hisi芯片采用了不同大小核的Processor cores：
Hi3519V100 Processor cores:（ARMV7-A）
A7 core @ 800MHZ
A17 core @ 1.2GHZ

Hi3519V101/Hi3559V100 Processor cores:（ARMV7-A）
A7 core @ 800MHZ
A17 core @ 1.5GHZ

Hi3559A V100Processor cores:（ARMV8-A）
One Single-core Cortex-A53 system and one dual-core Cortex-A73+dual-core Cortex-A53 big.LITTLE system.
One Cortex-M7 core,one GPU, two DSPs and one NNIE.

3、How to check core, frequency, features of CPU and memory infos

（1）查看cpu核数，特性等信息

cat /proc/cpuinfo

（2）查看CPU频率

# cat /proc/cpuinfo |grep MHz|uniq

注意：

在ARM设备板子上，可能由于系统进行了裁剪，不能直接查看cpu主频信息，下面进行了一些讨论：
https://stackoverflow.com/questions/32474101/how-to-get-cpu-clock-frequency-on-an-arm-linux-machine#
https://superuser.com/questions/406141/how-to-get-an-arm-cpu-clock-speed-in-linux
结论：
从分析来看，频率信息可能是在SOC其他部分提供的，不是有cpuinfo所提供，幸运的话可以通过计算估计得到frequency。

（3）查看内存信息

cat /proc/meminfo

（4）查看存型号、频率，使用命令(使用root才行)

dmidecode -t memory    //需要安装该命令才能使用

dmidecode命令可以让你在Linux系统下获取有关硬件方面的信息。dmidecode的作用是将DMI数据库中的信息解码，以可读的文本方式显示。由于DMI信息可以人为修改，因此里面的信息不一定是系统准确的信息。dmidecode遵循SMBIOS/DMI标准，其输出的信息包括BIOS、系统、主板、处理器、内存、缓存等等。

hwinfo          //查询硬件信息，需要安装该命令才能使用

（5）查看系统运行时间：

cat /proc/uptime

（6）查看内核版本：

cat /proc/version

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THE END!