cpu_percent（interval=None）总是返回0，而不考虑间隔值PYTHON

Question

无论间隔值如何，代码始终返回0.0值。

import psutil
p = psutil.Process()
print p.cpu_percent(interval=1)
print p.cpu_percent(interval=None)

Answer 1

根据我自己的代码：

cpu = psutil.cpu_times_percent(interval=0.4, percpu=False)

Answer 2

进程对象的cpu是可变的。我给你做了一些测试。

for i in range(10):
    p = psutil.Process(3301)
    print p.cpu_percent(interval=0.1)

结果： 9.9 0.0 0.0 0.0 0.0 9.9 0.0 9.9 0.0 0.0

所以如果你想得到一个进程对象的CPU百分比，你可以在一定时间内取平均值。

test_list = []
for i in range(10):
    p = psutil.Process(6601)
    p_cpu = p.cpu_percent(interval=0.1)
    test_list.append(p_cpu)
print float(sum(test_list))/len(test_list)

结果： 1.98

Answer 3

这种行为是documented：

When interval is 0.0 or None compares process times to system CPU times elapsed since last call, returning immediately. That means the first time this is called it will return a meaningless 0.0 value which you are supposed to ignore. In this case is recommended for accuracy that this function be called a second time with at least 0.1 seconds between calls.

还有一个警告，禁止对单个调用使用interval=None：

Warning: the first time this function is called with interval = 0.0 or None it will return a meaningless 0.0 value which you are supposed to ignore.

如果使用interval=None，请确保与以前的调用相比调用.cpu_percent。

p = psutil.Process(pid=pid)
p.cpu_percent(interval=None)
for i in range(100):
    usage = p.cpu_percent(interval=None)
    # do other things

而不是：

for i in range(100):
    p = psutil.Process(pid=pid)
    p.cpu_percent(interval=None)
    # do other things