linux下的ktime_t timeval timespec

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我是靠谱客的博主简单电话，最近开发中收集的这篇文章主要介绍linux下的ktime_t timeval timespec，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

内核中，经常看到ktime_t变量，总结下

ktime_t

 Nanosecond//纳秒
/* Nanosecond scalar representation for kernel time values */
typedef s64	ktime_t;

ktime_t n等于n纳秒

有ms/ns转换成ns的两个函数，是不是很简单

static inline ktime_t ns_to_ktime(u64 ns)
{
	return ns;
}

static inline ktime_t ms_to_ktime(u64 ms)
{
	return ms * NSEC_PER_MSEC;
}

类似的函数

static inline ktime_t ktime_set(const s64 secs, const unsigned long nsecs)
{
	if (unlikely(secs >= KTIME_SEC_MAX))
		return KTIME_MAX;

	return secs * NSEC_PER_SEC + (s64)nsecs;
}

include/linux/time64.h
#define MSEC_PER_SEC    1000L
#define USEC_PER_MSEC   1000L
#define NSEC_PER_USEC   1000L
#define NSEC_PER_MSEC   1000000L
#define USEC_PER_SEC    1000000L
#define NSEC_PER_SEC    1000000000L
#define FSEC_PER_SEC    1000000000000000LL

反过来，ktime_t转换成us/ms

static inline s64 ktime_to_us(const ktime_t kt)
{
	return ktime_divns(kt, NSEC_PER_USEC);
}

static inline s64 ktime_to_ms(const ktime_t kt)
{
	return ktime_divns(kt, NSEC_PER_MSEC);
}

timeval

struct timeval {
        __kernel_time_t         tv_sec;         /* seconds */
        __kernel_suseconds_t    tv_usec;        /* microseconds */微秒
};

void do_gettimeofday(struct timeval *tv)
{
	struct timespec64 now;

	getnstimeofday64(&now);
	tv->tv_sec = now.tv_sec;
	tv->tv_usec = now.tv_nsec/1000;
}

timespec

#ifndef _STRUCT_TIMESPEC
#define _STRUCT_TIMESPEC
struct timespec {
        __kernel_time_t tv_sec;                 /* seconds */
        long            tv_nsec;                /* nanoseconds */
};
#endif

/* Map the ktime_t to timespec conversion to ns_to_timespec function */
#define ktime_to_timespec(kt)		ns_to_timespec((kt))

/* Map the ktime_t to timespec conversion to ns_to_timespec function */
#define ktime_to_timespec64(kt)		ns_to_timespec64((kt))

/* Map the ktime_t to timeval conversion to ns_to_timeval function */
#define ktime_to_timeval(kt)		ns_to_timeval((kt))

/* Convert ktime_t to nanoseconds - NOP in the scalar storage format: */
#define ktime_to_ns(kt)			(kt)

获取内核启动总时间

long long  s=0;
long long  ms=0;
ms=ktime_to_ms(ktime_get_boottime());
printk("boottime=%lld msn",ms);
s=ms/1000;
ms=ms%1000;
printk("boottime=%lld.%lld sn",s,ms);

测量时间流逝

#include<linux/module.h>
#include<linux/ktime.h>
#include<linux/delay.h>   

ktime_t time_start;
struct timeval tstart,tend;
s64 elapsed_ns=0;    
static int time_init(void)  
{  
	time_start=ktime_get();
	msleep(1);
	elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start)); 
	printk("%lld nsn",elapsed_ns);

	do_gettimeofday(&tstart);
	msleep(1);
	do_gettimeofday(&tend);
	printk("time taken: %ld millisecn",1000 * (tend.tv_sec - tstart.tv_sec) +(tend.tv_usec - tstart.tv_usec) / 1000);
	return 0;  
}  
      
static void time_exit(void)  
{  
	printk(KERN_INFO "%sn",__FUNCTION__);  
}  
      
module_init(time_init);  
module_exit(time_exit);
MODULE_LICENSE("GPL");