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

[zeljko]

On Wednesday 02 of November 2011 14:55:36 michael.vancanneyt at wisa.be wrote:
> 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)

Then just remove code which uses NowLibc() , and use clock_gettime() ... if 
Libc isn't available .... maybe it should be libc ... dunno.

zeljko


> 
> Michael.
> _______________________________________________
> fpc-devel maillist  -  fpc-devel at lists.freepascal.org
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