ARM EAS Overview
EAS全称是Energy Aware Scheduling，主要目标就是降低功耗同时兼顾性能，专门针对异构CPU，比如Arm大小核架构。EAS利用task load(PELT or WALT) 和 Engery Model (EM) 找到engergy-efficient CPU。这里的PELT是per-entity load tracking，上游Linux使用。QCO...阅读全文
分析erofs-utils canned fs_config查找失败问题
H的erofs已经支持Android，QC/droid 10下生成镜像有如下错误：failed to find [app] in canned fs_configcode在system/core/libcutils/canned_fs_config.cpp:void canned_fs_config(const char* path, int dir, const cha...阅读全文
超慢速电影播放相框
How cool would this be playing your favourite film onto a plain wall somewhere you can see it throughout the day?库布里克的2001是真慢放动画美美滴背面btw: 没必要pi 4，pi zero就够了，cpu会高一点，稍微改改脚本参考https://make.q...阅读全文
Kernel Panic实例分析三 : Unable to handle kernel paging request
QC armv7平台kernel 4.x出现的死机问题，一开始很随机以为是DDR硬件问题，直到后面死机越來越多，还出现过pc一样的现场，让人不得不怀疑是SW issue，同步提给QC看，看QC的答复就是用tracer32来定位的，下来温习了下armv7，完全可以用red hat的crash工具结合反汇编和源码分析定位，对小厂算是节约license成本了?我们先看死机现场:...阅读全文
How to get kaslr offset on ARM64
Red Hat的crash工具有个option是--kaslr，一般解析ramdump会用，工具定义：--kaslr offset | auto If x86, x86_64 or s390x kernel was configured with CONFIG_RANDOMIZE_BASE, the offset value is equal to the dif...阅读全文
Kernel Panic实例分析二 : Null pointer
QCOM安卓armv7 smp平台, kernel 4.x。死机时dmesg:[ 4.790798] Unable to handle kernel NULL pointer dereference at virtual address 000001e0
[ 4.790803] pgd = edfd65c2
[ 4.790807] [000001e0] ...阅读全文
How to build Red Hat Crash for ARM under x86_64 Ubuntu
Now, our building environments for Android are almost x86_64 Ubuntu, but we still have low-end products based on armv7 kernel. For analyze ramdump under armv7, let's build it on Ubuntu 18...阅读全文
了解Android 10 DSU
DSU(Dynamic System Updates)是Android 10引入的一个feature。先了解下GSI。GSIGSI(Generic System Image)看字面就是通用的系统镜像了，就是Google官方Android，没有设备制造商(如某米)的自定义修改。Android 9开始就能用了，是for app开发。官方给的说明是：The GSI projec...阅读全文