[fpc-devel] Problem with Now() and time changed by ntpd

[michael.vancanneyt at wisa.be]

On Wed, 2 Nov 2011, michael.vancanneyt at wisa.be wrote:

>
>
> On Wed, 2 Nov 2011, zeljko wrote:
>
>> On Wednesday 02 of November 2011 11:23:10 michael.vancanneyt at wisa.be wrote:
>>> On Wed, 2 Nov 2011, Jonas Maebe wrote:
>>>> Marco van de Voort wrote on Wed, 02 Nov 2011:
>>>>> The point was just some encouragement to look further than the immediate
>>>>> need though, and keep the time call relatively cheap. That doesn't
>>>>> exclude being correct, it just means a more elaborate implementation.
>>>> 
>>>> I do not think that reporting the time correctly taking into account the
>>>> current time zone and daylight savings time is a function that needs to
>>>> be treated as performance-critical.
>>> 
>>> Under some (not so uncommon) circumstances it is, e.g. for logging
>>> facilities. Our own eventlog facility would suffer from this.
>>> 
>>>>> But harddisk latency can easily be in the half a second to second
>>>>> magnitude (and then I don't even count spindowns, and am I accessing
>>>>> directories that I continously access).
>>>> 
>>>> If you are stat'ing that file for changes all the time, either the result
>>>> will be cached or the hard drive won't spin down. And stat'ing a file
>>>> will not take half a second when done repeatedly.
>>> 
>>> I tested this yesterday, using the following sequence:
>>> 
>>> fpGettimeOfDay();
>>> if UseStat then
>>>    fpStat('/etc/timezone');
>>> fpGetTimeOfDay();
>> 
>> Please see results about Now() and something that I've mentioned about
>> deprecitation of gettimeofday().According to this test, current
>> fpgettimeofday() is crap when compared with clock_gettime() (kernel) or 
>> libc
>> calls (I've copied scenario from kylix sysutils).
>> 
>> *Kernel clock_gettime() NowReal() with 10000000 calls = 4870 ms
>

and anyway:

fsb: >fpc /home/michael/unixclocks.lpr
Fatal: Can't find unit Libc used by unixclocks
Fatal: Compilation aborted
Error: /usr/local/bin/ppcx64 returned an error exitcode (normal if you did not specify a source file to be compiled)

Michael.