4,vsyscall LWN上有所介绍,https://lwn.net/Articles/446528/ The vsyscall area is the older of these two mechanisms. It was added as a way to execute specific system calls which do not need any real level of privilege to run. The classic example is gettimeofday(); all it needs to do is...
Qp0zCvtToMITime()--Convert Timeval Structure to _MI_ Time settimeofday()--Set System Clock Example The following example gets the current UTC time. Note:By using the code examples, you agree to the terms of theCode license and disclaimer information. Example Output:...
C compilers may support additional specifiers and modifiers for the format parameter of this function, which are not described here. Example /* strftime example */#include <stdio.h>#include int main (){ time_t rawtime; struct tm * timeinfo; char buffer [80]; time ( &rawtime ); timein...
Now, let’s see an example to illustrate these principles. #include <stdio.h> #include #define NUM 1000000 #define NUM2 10000000 void loopFunc(size_t num) { int tmp = 0; for (int i = 0; i < num; ++i) { tmp += 1; } } int main() { clock_t start_time, end_time; ...
MODULE_DESCRIPTION("A simple example Linux module."); 在上面的代码中,我们定义了一个名为my_module_init的初始化函数,在该函数中调用了do_gettimeofday来获取当前时间,并使用printk函数将其打印到内核日志中。这个例子非常简单,但它展示了如何在内核模块中使用do_gettimeofday函数。 三、注意事项和其他替代函数 1...
gettimeofday()是一个系统调用函数,用于获取当前的系统时间。它的原型如下: ```c int gettimeofday(struct timeval *tv, struct timezo...
modern Intel chips. Unlike other timing methods, the TSC remains synchronized across cores and unaffected by frequency scaling, making it a reliable global time source. To demonstrate its usage, you can refer to the provided example along with a detailed explanation of the accompanying assembly ...
For example, this format string "%Y-%m-%d %H:%M:%S" specifies the date and time in this form: 2001-01-14 13:09:42 Pass strftime a character buffer to receive the string, the length of that buffer, the format string, and a pointer to a struct tm variable. See the strftime man ...
It is not guaranteed to be any amount of time since a fixed epoch; it might, for example, be seconds since boot time, so you can use it to calculate time intervals, but not the date-plus-UTC of an event. Note also that the clock_gettime() man page says: CLOCK_MONOTONIC clock tha...