武城3版本镜像更新说明

武城3是GDK8的安卓版本镜像，主要为了方便在安卓平台上进行开发调试的工程师进行学习和研究。

主要改动：

1. 增加perf、sysstat、simpleperf、gdbserver、atrace等常用工具。

武城3版本的镜像新增加了许多工具，这里主要介绍一下perf和GDBServer。

perf：

Perf是从Linux 2.6开始引入的一个profiling工具，通过访问包括pmu在内的软硬件性能计数器来分析性能，支持
多架构，是目前Kernel的主要性能检测手段，和Kernel代码一起发布，所以兼容性良好。

perf的命令列表：

rk3328_box:/ # perf
usage: perf [‐‐version] [‐‐help] COMMAND [ARGS]
The most commonly used perf commands are:
annotate          Read perf.data (created by perf record) and display annotated code
archive           Create archive with object files with build‐ids found in perf.data file
bench             General framework for benchmark suites
buildid‐cache     Manage <tt>build‐id</tt> cache.
buildid‐list      List the buildids in a perf.data file
diff              Read two perf.data files and display the differential profile
inject            Filter to augment the events stream with additional information
kmem              Tool to trace/measure kernel memory(slab) properties
kvm               Tool to trace/measure kvm guest os
list              List all symbolic event types
lock              Analyze lock events
probe             Define new dynamic tracepoints
record            Run a command and record its profile into perf.data
report            Read perf.data (created by perf record) and display the profile
sched             Tool to trace/measure scheduler properties (latencies)
script            Read perf.data (created by perf record) and display trace output
stat              Run a command and gather performance counter statistics
test              Runs sanity tests.
timechart          Tool to visualize total system behavior during a workload
top              System profiling tool.
See 'perf help COMMAND' for more information on a specific command.