How to build mkfs.erofs for ARM64
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 development ...阅读全文
如何测试cpufreq setpolicy driver
上一篇说过有个cpufreq setpolicy patch涉及验证，qemu intel_pstate是不行了，主要是不支持X86_FEATURE_HWP or X86_FEATURE_APERFMPERF，只能在物理机上测试了。我的本本是E40(一代i3)，用了有点久了也不支持，intel_pstate是for SandyBridge arch，Intel从二代 i3...阅读全文
如何用QEMU运行x86 kernel
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，also vb under...阅读全文
CPUFreq policy代码分析
参考4.9，主要了解几个结构成员：struct cpufreq_policy {
/* CPUs sharing clock, require sw coordination */
cpumask_var_t cpus; /* Online CPUs only */
cpumask_var_t related_cp...阅读全文
CPUFreq boost代码分析
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 whole chip i...阅读全文
Linux CPUFreq Subsystem Overview
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 processor switch between va...阅读全文