如何在python中获得单调的持续时间? [英] How do I get monotonic time durations in python?

问题描述

我想记录实际时间在墙上花费多长时间.目前，我正在这样做:

I want to log how long something takes in real walltime. Currently I'm doing this:

startTime = time.time()
someSQLOrSomething()
print "That took %.3f seconds" % (time.time() - startTime)

但是，如果在运行SQL查询(或任何其他查询)时调整了时间，那将失败(产生错误的结果).

But that will fail (produce incorrect results) if the time is adjusted while the SQL query (or whatever it is) is running.

我不想仅仅对其进行基准测试.我想将其登录到实时应用程序中，以查看实时系统上的趋势.

I don't want to just benchmark it. I want to log it in a live application in order to see trends on a live system.

我想要诸如clock_gettime(CLOCK_MONOTONIC，...)之类的东西，但是在Python中.并且最好不必编写一个调用clock_gettime()的C模块.

I want something like clock_gettime(CLOCK_MONOTONIC,...), but in Python. And preferably without having to write a C module that calls clock_gettime().

推荐答案

该函数非常简单，您可以使用ctypes来访问它:

That function is simple enough that you can use ctypes to access it:

#!/usr/bin/env python

__all__ = ["monotonic_time"]

import ctypes, os

CLOCK_MONOTONIC_RAW = 4 # see <linux/time.h>

class timespec(ctypes.Structure):
    _fields_ = [
        ('tv_sec', ctypes.c_long),
        ('tv_nsec', ctypes.c_long)
    ]

librt = ctypes.CDLL('librt.so.1', use_errno=True)
clock_gettime = librt.clock_gettime
clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]

def monotonic_time():
    t = timespec()
    if clock_gettime(CLOCK_MONOTONIC_RAW , ctypes.pointer(t)) != 0:
        errno_ = ctypes.get_errno()
        raise OSError(errno_, os.strerror(errno_))
    return t.tv_sec + t.tv_nsec * 1e-9

if __name__ == "__main__":
    print monotonic_time()

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