Window VS Linux : timer question

chanwing · 03-29-2005, 02:02 AM

Hello,
Can anyone help me to solve this problem?
I wanna convert a timer file from a window program(VC++6.0) into Linux.
There are "GetTickCount(),QueryPerformanceFrequency(),QueryPerformanceCounter()".

GetTickCount() return number of milliseconds that have elapsed since the system was started.
QueryPerformanceFrequency() retrieves the frequency of the high-resolution performance counter.
QueryPerformanceCounter() retrieves the current value of the high-resolution performance counter.

How can I create three functions to replace them ?
I had already change the GetTickCount() but I don't know is it correct or not.

#include <sys/time.h>
unsigned int Timer::GetTickCount()
{
timeval t;
if (gettimeofday(&t,NULL)==0)
return t.tv_usec;
}

I saw the "sys/time.h","sys/times.h","time.h","linux/times.h","linux/time.h" and "linux/timer.h" but I still don't have any idea for replacing QueryPerformanceFrequency() and QueryPerformanceCounter().
I would be gratefully if you can help me to solve the problem
Thanks

Marius2 · 03-29-2005, 06:11 AM

unsigned int Timer::GetTickCount()
{
unsigned int result=0;
timeval gtod_now_time;
gettimeofday(&gtod_now_time,0);
result=(gtod_now_time.tv_usec-gtod_start_time.tv_usec)/1000;
result+=(gtod_now_time.tv_sec-gtod_start_time.tv_sec)*1000;
return result;
}

No idea about the Query... functions, sorry.

chanwing · 03-29-2005, 07:06 PM

Thank you very much "Marius2 " for your help and reply.

But, I am not really understand your program.

the variable "gtod_start_time.tv_usec" is come from where?
is it "gettimeofday(&gtod_start_time,0);" called in other place?

In fact, what is the different between gtod_start_time and gtod_now_time?

GetTickCount return millisecond (in window original function)but tv_usec return microsecond(in linux time.h). micro=1/1000milli. is it "*1000" not "/1000"?

QueryPerformanceFrequency() and QueryPerformanceCounter() are really difficult to migrate to Linux.

Do anyone know any functions or methods that can get the CPU counter values in Linux?
thx

Marius2 · 03-30-2005, 12:49 AM

Quote:

Originally posted by chanwing
Thank you very much "Marius2 " for your help and reply.

But, I am not really understand your program.

the variable "gtod_start_time.tv_usec" is come from where?
is it "gettimeofday(&gtod_start_time,0);" called in other place?

In fact, what is the different between gtod_start_time and gtod_now_time?

Ok sorry, I missed that. gtod_start_time is a member variable of the class and set in the constructor. If it's instantiated at program start time, this method will return milliseconds since the start of the program. If you really need milliseconds since the start of the system, you might need to write a small program which dumps the gettimeofday value to a text file at boot time (called in /etc/init.d/rc3.d, or whatever runlevel), which is then read once by your code, etc. etc. There may be other ways, but that is the only way I can think of now.

Quote:

[i]
GetTickCount return millisecond (in window original function)but tv_usec return microsecond(in linux time.h). micro=1/1000milli. is it "*1000" not "/1000"?

Look at it again, the unit you want is milliseconds.

chanwing · 03-30-2005, 07:25 PM

OH, I see.
Thank you very much.
Are there any log files that the Linux will record the time when the linux system startup? If I am right, I remember that everytime the Linux will record any processes in a log file just like a command of "history".
Do you know where can I find out more information about timer in Linux? I found some Linux books but they talk less about it.
Sorry that I have lots of questions.

Marius2 · 03-31-2005, 02:22 AM

No idea about the logs, but you may want to take a look at /var/log directory. A simple shell script containing something like "echo $(/sbin/hwclock) > /tmp/starttime.txt" and invoked at start time via a symlink in /etc/init.d/rc[n].d may also do the trick.

BTW when I'm looking for *NIX aquivalents of windows interfaces, my first try generally is asking google for something like "<name_of_windows_api> linux"

HTH

chanwing · 03-31-2005, 06:20 PM

oh, thanks.
thank you for your useful information.

I have an other additional question.
do you know Mfc Macros ?
I have a problem about the rewrite of IMPLEMENT_DYNCREATE(), DECLARE_DYCREATE() and DECLARE_DYNAMIC().
Can you give me some ideas about it?

jlliagre · 03-31-2005, 07:05 PM

Quote:

Are there any log files that the Linux will record the time when the linux system startup?

Code:

last -1 reboot

should tell you that.

chanwing · 04-01-2005, 02:32 AM

Thank you jlliagre.
and Thanks to ALL.

jonaskoelker · 04-01-2005, 11:52 AM

have a look at the shell command `uptime', and the source for it.

hth --Jonas Kölker

jlliagre · 04-01-2005, 12:38 PM

Both last and uptime use the /var/run/utmp(x) file.

jonaskoelker · 04-02-2005, 06:15 PM

Quote:

Both last and uptime use the /var/run/utmp(x) file.

man last: `last searches back through the file /var/log/wtmp'
man uptime: `FILES: /var/run/utmp [...]'

Code:

$ last -1 reboot

wtmp begins Fri Apr  1 18:35:49 2205
$ uptime
 02:06:53 up 3 days,  7:19,  3 users,  load average: 0.34, 0.24, 0.66
$ date
(apr 3)

you don't have to be an expert in time arithmetic to see that there's a mismatch between `last' and `uptime'.

I trust uptime, since I know that I didn't reboot on April 1st (no joke

).

YMMV(!)

--Jonas Kölker

jlliagre · 04-03-2005, 04:35 AM

Well, Linux is (or some Linux distros are) rotating or clearing /var/log/wtmp every month, which is questionable (Unix keep the file intact).
Anyway, you can overcome it by pointing "last" to a more persistent file.

Code:

last -1 reboot -f /var/run/utmp

chanwing · 04-05-2005, 04:27 AM

Oh.......Thank you very much

I have seen a book "Linux Device Drivers, 2nd Edition, Orelly" recently.

#include <linux/timex.h>
cycles_t get_cycles(void);

The function is defined for the platform has cycle-counter register

do any one know about "jiffies"?
it is also for the time.

I still read the book and I will try to write a test program for testing the time.