mkfs.erofs is a user-space tool to create erofs filesystem images.
erofs是华为为了增强安卓性能提出的自研文件系统，其内核文档提到用户态工具:
The following git tree provides the file system user-spacetools under ...
最近在提交cpufreq patch，稍微有点逻辑改动的Rafael都要你test, test。有个改动涉及setpolicy driver，要验证，第一印象就是用qemu。
让我们来看下如何搭环境(initrd=ramdisk):
my linux server(xeon) for building can not access internet...
参考4.9内核，还是先看文档描述：
IntroductionSome CPUs support a functionality to raise the operating frequency ofsome cores in a multi-core package if certain conditions apply, mostlyif the who...
参考4.9，CPUFreq即CPU Frequency scaling或者CPU performance scaling，允许你运行时改变CPU clock speed.
文档路径: ./Documentation/cpu-freq/，先来看几个概念：
Some CPU frequency scaling-capable pr...