转自：http://www.igigo.net/post/xiao-za-sui/-proc-statde-cpufu-zai-xin-xi-shuo-ming
关于/proc/stat最正确的文档
首先给出/proc/stat原始的文档, 其它文档都是从这文档翻译或引申出来, 如果看得明E文文档, 这最好不过
进程的nice，进程的nice值一般是-20～19，他影响的是cpu分配给进程的时间片
对nice值一个形象比喻，假设在一个CPU轮转中，有2个runnable的进程A和B，如果他们的nice值都为0，假设内核会给他们每人分配1k个cpu时间片。但是假设进程A的为0，但是B的值为-10，那么此时CPU可能分别给A和B分配1k和1.5k的时间片。故可以形象的理解为，nice的值影响了内核分配给进程的cpu时间片的多少，时间片越多的进程，其优先级越高
/proc/stat
kernel/system statistics. Varies with architecture. Common
entries include:
cpu 3357 0 4313 1362393
The amount of time, measured in units of USER_HZ
(1/100ths of a second on most architectures, use
sysconf(_SC_CLK_TCK) to obtain the right value), that
the system spent in various states:
user (1) Time spent in user mode.
nice (2) Time spent in user mode with low priority
(nice).
system (3) Time spent in system mode.
idle (4) Time spent in the idle task. This value
should be USER_HZ times the second entry in the
/proc/uptime pseudo-file.
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete.
irq (since Linux 2.6.0-test4)
(6) Time servicing interrupts.
softirq (since Linux 2.6.0-test4)
(7) Time servicing softirqs.
steal (since Linux 2.6.11)
(8) Stolen time, which is the time spent in
other operating systems when running in a
virtualized environment
guest (since Linux 2.6.24)
(9) Time spent running a virtual CPU for guest
operating systems under the control of the Linux
kernel.
guest_nice (since Linux 2.6.33)
(10) Time spent running a niced guest (virtual
CPU for guest operating systems under the
control of the Linux kernel).
page 5741 1808
The number of pages the system paged in and the number
that were paged out (from disk).
swap 1 0
The number of swap pages that have been brought in and
out.
intr 1462898
This line shows counts of interrupts serviced since
boot time, for each of the possible system interrupts.
The first column is the total of all interrupts
serviced ncluding unnumbered architecture specific
interrupts; each subsequent column is the total for
that particular numbered interrupt. Unnumbered
interrupts are not shown, only summed into the total.
disk_io: (2,0):(31,30,5764,1,2) (3,0):...
(major,disk_idx):(noinfo, read_io_ops, blks_read,
write_io_ops, blks_written)
(Linux 2.4 only)
ctxt 115315
The number of context switches that the system
underwent.
btime 769041601
boot time, in seconds since the Epoch, 1970-01-01
00:00:00 +0000 (UTC).
processes 86031
Number of forks since boot.
procs_running 6
Number of processes in runnable state. (Linux 2.5.45
onward.)
procs_blocked 2
Number of processes blocked waiting for I/O to
complete. (Linux 2.5.45 onward.)出自: http://man7.org/linux/man-pages/man5/proc.5.html
常见的错误解释
参数 解释
user 从系统启动开始累计到当前时刻，用户态的CPU时间（单位：jiffies） ，不包含nice值为负进程。1jiffies=0.01秒
nice 从系统启动开始累计到当前时刻，nice值为负的进程所占用的CPU时间（单位：jiffies）
system 从系统启动开始累计到当前时刻，核心时间（单位：jiffies）
idle 从系统启动开始累计到当前时刻，除硬盘IO等待时间以外其它等待时间（单位：jiffies）
iowait 从系统启动开始累计到当前时刻，硬盘IO等待时间（单位：jiffies） ，
irq 从系统启动开始累计到当前时刻，硬中断时间（单位：jiffies）
softirq 从系统启动开始累计到当前时刻，软中断时间（单位：jiffies）/proc/stat的CPU负载信息说明
| 参数 | 说明 |
|---|---|
| user | 用户态的CPU时间, 从英文文档中我们可以看出, 并没有其它附加说明, 不包含nice值为负进程这种说法是错误的 |
| nice | 原文的意思是: 低优先级程序所占用的用户态的CPU时间, 对于nice值, 低优先级的nice值为正, 所以nice值为负的进程所占用的CPU时间的说法是错误的 |
| system | 系统态的CPU时间 |
| idle | CPU空闲的时间(不包含IO等待) |
| iowait | 等待IO响应的时间 |
| irq | 处理硬件中断的时间 |
| softirq | 处理软中断的时间 |
测试验证
除了nice, 其它段没多少问题, 多数文章说
nice是nice值为负的进程所占用的CPU时间我特意找一台机做了测试
- 初始时, nice段数据为0, 用nice值-20来跑下cpu压力程序, nice数据没有变化, 一直为0;
- 重新用nice值为20来跑cpu压力程序, nice数据直接增长
连接：计算loading的源码：
https://github.com/feifeiyuan/script/tree/master/C_program/proc_stat%E4%B8%8B%E7%9A%84cpu_work_load