一、top命令
adb shell top --help
usage: top [-Hbq] [-k FIELD,] [-o FIELD,] [-s SORT] [-n NUMBER] [-d SECONDS] [-p PID,] [-u USER,]
Show process activity in real time.
-H Show threads
-k Fallback sort FIELDS (default -S,-%CPU,-ETIME,-PID)
-o Show FIELDS (def PID,USER,PR,NI,VIRT,RES,SHR,S,%CPU,%MEM,TIME+,CMDLINE)
-O Add FIELDS (replacing PR,NI,VIRT,RES,SHR,S from default)
-s Sort by field number (1-X, default 9) 选择根据某项（cpu,vss,rss,thr）来排序
-b Batch mode (no tty)
-d Delay SECONDS between each cycle (default 3)
更新的时间间隔，默认是每隔3s更新下状态，top -d 0时会持续地输出，不过很占CPU。
-n Exit after NUMBER iterations 显示n次top的结果后命令就会退出
-p Show these PIDs
-u Show these USERs
-q Quiet (no header lines)
Cursor LEFT/RIGHT to change sort, UP/DOWN move list, space to force
update, R to reverse sort, Q to exit.
adb shell top
[?25l[0m[H[J[s[999C[999B[6n[uTasks: 445 total, 1 running, 435 sleeping, 0 stopped, 2 zombie
Mem: 2866500k total, 2794280k used, 72220k free, 77912k buffers
Swap: 520908k total, 315604k used, 205304k free, 978836k cached
800%cpu 14%user 0%nice 29%sys 757%idle 0%iow 0%irq 0%sirq 0%host
PID USER PR NI VIRT RES SHR S [%CPU] %MEM TIME+ ARGS [0m
14357 shell 20 0 10M 2.1M 1.4M R 22.8 0.0 0:00.13 top
12739 root 20 0 0 0 0 S 2.8 0.0 0:05.11 [kworker/u16:2]
11967 root 0 -20 0 0 0 S 2.8 0.0 0:00.91 [kworker/u17:1]
7704 u0_a127 20 0 1.7G 65M 47M S 2.8 2.3 1:20.68 com.tencent.mob+
VIRT：虚拟内存，假如进程申请10m的内存，但实际只使用了5m，那么它会增长10m，而不是实际的使用量。
RES：常驻内存，进程当前使用的内存大小，但不包括swap out。
SHR：共享内存，除了自身进程的共享内存，也包括其他进程的共享内存
计算某个进程所占的物理内存大小公式：RES – SHR