[Melbourne-pm] DateTime::new

Tim Connors tconnors at astro.swin.edu.au
Sun Dec 9 16:49:38 PST 2007

I've got code that makes extensive use of DateTime::new via 
DateTime->from_epoch() and 

I've recently noticed a rather large regression in speed of these calls 
(factors of many).  I don't think it's the actual modules, since I hadn't 
touched CPAN in quite some time, and I recall having upgraded my 
distribution's perl in the past to version 5.8.8 I think (from somewhere 
around 5.8.0), balking at the speed of these calls, downgrading back to 
whereever it came from and seeing the speed go back to a good healthy 
speed again.

However, looks like the distribution (centos 4 == redhat enterprise 4) has 
forced an upgrade of perl to 5.8.8 this time, and I get the slow DateTime 
calls again.

Would anyone have any idea as to what might have changed?

The results of dprofpp -u -p:
 55.9   24.11 30.600  17409   0.0014 0.0018  DateTime::new
 7.67   3.306  3.478  17908   0.0002 0.0002  Params::Validate::_validate
 7.15   3.079 33.580   8686   0.0004 0.0039  DateTime::Format::Strptime::parse_
(and I believe the DateTime::new is coming almost exclusively from 
DateTime::Format::Strptime::parse_datetime in this case, so it must be 
initialising it twice for whatever reason)

I've tried with a floating timezone, UTC, GMT, local and they're all 
equally slow.

I tried stepping through with perl -d, and it's not obvious yet to me 
where the expensive calls are done (I need to work out how to tell DProf 
to dig down into the calls DateTime makes).  The most obvious location 
would be Time::Local::timegm_nocheck, since everything prior to that is 
just trivial manipulations of the supplied string.

Both versions of the following test out as quick:

DateTime                       0.36      0.41  DROLSKY/DateTime-0.41.tar.gz
DateTime::Format::Strptime    1.0700    1.0702  RICKM/DateTime-Format-Strptime-1.0702.tgz
DateTime::Locale               0.34      0.35  DROLSKY/DateTime-Locale-0.35.tar.gz
DateTime::TimeZone             0.62      0.70  DROLSKY/DateTime-TimeZone-0.70.tar.gz

Any ideas of where to go from here?

Tim Connors

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