Silly precision in a timing macros

[Stanley Hopcroft]

Dear Folks,

On Thu, Oct 28, 2004 at 03:59:31PM -0700, Jason Martin wrote:
> On Thu, Oct 28, 2004 at 05:47:50PM -0500, Ethan Galstad wrote:
> > > The precision provided by timing macros (for latency and executin
> > > times) are a bit silly, since it holds room for 6 decimal points but
> > > only ever uses 3 of them (a limit in the Linux kernel, I've heard).

Timer resolution this may be a platform dependent ability.

> I'm surprised about that; some of my perl scripts can print time
> periods to 6 decimal points.
> 
> The perl module is Time::HiRes.
> If I do something like this:
> 

I think you will find that this module is an XS (Perl eXtension) that 
calls the system's gettimeofday(), a function that may not be POSIX and 
whose resolution varies.

> #Track execution time
> my $t0 = [gettimeofday];
> //[misc stuff]
> print "Stored data for $var on $var2 in " . tv_interval($t0);
> 
> , I can get output such as:
> Stored data for ****** on ****** in 0.004562s
> 
> Perhaps there is some other limitation causing the time
> precision to be lowered?

BSD systems have a gettimeofday that returns microsecs.

Do you really need this accuracy ?

Milliseconds are fine for me. Prob Seconds are also.

> 
> -Jason Martin

Yours sincerely.


-- 
Stanley Hopcroft

Network specialist, IT Infrastructure
IP Australia
Ph: (02) 6283 3189  Fax: (02) 6281 1353
PO Box 200 Woden  ACT 2606
http://www.ipaustralia.gov.au
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