Re: [coLinux-users] Very large time offset in coLinux

[Ron A. <ra...@ho...>]

Hi Henry,

Can you please explain why you multiply by 100 in 

timestamp_diff += 100 * (((long long)timestamp.quad) - ((long long)cmon->timestamp.quad));  /* HZ value */



http://colinux.svn.sourceforge.net/viewvc/colinux/branches/devel/src/colinux/os/winnt/kernel/lowlevel/time.c?view=markup#l31

If this function is called every 100ms, as you previously wrote, then you get 10 jiffies per call. Shouldn't it be 1 jiffy per 100ms? Shouldn't you multiply by 10 instead?

I guess your calculation is right, but I can't figure it out.

Thanks,
Ron

Date: Fri, 3 Sep 2010 00:42:47 +0200
From: hen...@ar...
To: ra...@ho...
CC: col...@li...
Subject: Re: [coLinux-users] Very large time offset in coLinux



  


    
    Message body
  
  
    Hello Ron,

    

    we don't use RDTSC directly. We use windows API, and that should
    work without problems. KeQueryPerformanceCounter is the only
    function with smallest time interval. Of curse I also have seen
    updates for broken KeQueryPerformanceCounter:
    http://support.microsoft.com/kb/896256

    

    The problem is not to follow the time. If the timediff is more as
    one second, for example if you suspend Windows, then we set the time
    absolutely. The problem is, from where we can get the exact time
    stamp, if KeQueryPerformanceCounter is wrong?

    

    Here we have the two calculations. One on Windows side, here we
    calculate the difference of "jiffies" in callback_return_jiffies:

    http://colinux.svn.sourceforge.net/viewvc/colinux/branches/devel/src/colinux/kernel/monitor.c?view=markup#l366

    

    co_os_get_timestamp is here:

http://colinux.svn.sourceforge.net/viewvc/colinux/branches/devel/src/colinux/os/winnt/kernel/lowlevel/time.c?view=markup#l31

    

    On Linux side we increment teh jiffies and time here in function co_handle_jiffies:

http://colinux.svn.sourceforge.net/viewvc/colinux/branches/devel/patch/base-2.6.33.diff?view=markup#l2563

    

    I will create more debug for cases of "time warps".

    

    --

    Henry