-DNOPROFILE with make buildworld...

Harrison Peter CSA BIRKENHEAD peter.harrison at dwp.gsi.gov.uk
Wed Jun 22 09:03:42 GMT 2005

> -----Original Message-----
> From: Chuck Swiger [mailto:cswiger at mac.com]
> Sent: 21 June 2005 19:25
> To: Roland Smith
> Cc: Harrison Peter CSA BIRKENHEAD; freebsd-questions at freebsd.org
> Subject: Re: -DNOPROFILE with make buildworld...

> Normally, you don't use the profiled versions of libraries 
> unless you are 
> running a binary which links against them.  If you are 
> running a binary which 
> has not been compiled with profiling, the toolchain will link 
> it against normal 
> versions of the libraries.

Most of the apps I'm running have been compiled from ports against the stock 5.3-RELEASE libraries. Are the stock libraries profiling or not? Would I have had to explicitly set an option to compile ports to link against profiling libraries? Is it therefore a reasonable assumption that if I didn't specifically make any binaries profiling, then they'll be not-profiling?

> [ ... ]
> > Programs that have been compiled with profiling enabled might run
> > fractionally slower that without. But I doubt the difference is
> > significant on a modern machine. 
> The amount of overhead seems to vary by platform, but it's 
> generally only a 
> couple of percent.  Not very significant, but maybe noticable.
> The major downsides to having profiled libraries around is 
> that they use more 
> disk space than normal versions, and it takes longer to do a 
> buildworld, but 
> the runtime performance of the system for normal binaries 
> will not be affected.

I can live with that kind of performance overhead, but disk space is more of an issue for me.

> > I'll be bold and say that modern machines are so fast that there is
> > seldom need to profile a program.
> Even people who write code on fast machines may run that code 
> on slower boxes 
> sometime.  However, what you've said is still true: there is 
> seldom need to 
> profile a program.  Get it working well enough that it 
> doesn't leak memory, and 
> then worry about profiling it.  :-)

Indeed. Once I've successfully upgraded my Athlon XP 1800+ desktop to 5.4 I'm intending to set up NFS shares and upgrade my Thinkpad 600e which is also on 5.3 (and I don't fancy building world on it's P2 366).

> -- 
> -Chuck

Thanks for the advice.

Peter Harrison

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