-DNOPROFILE with make buildworld...

Roland Smith rsmith at xs4all.nl
Tue Jun 21 18:06:50 GMT 2005

On Tue, Jun 21, 2005 at 01:49:06PM +0100, Harrison Peter CSA BIRKENHEAD wrote:

> I've cvsup'ed my source tree, and stepping through the instructions in
> the handbook I note that it recommends running make buildworld with
> -DNOPROFILE (or specifying it in make.conf). I'm not clear what the
> impact of running profiled libraries is against non-profiled
> libraries. I've done a quick search via google and through the list
> archives without success.

It's not about profiled libraries, but profiling libraries. Let me explain.

Programs that are compiled with profiling enabled gather data about
their run-time behaviour, and write that to a file, usualy gmon.out. If
the program is linked to a profiling library, data about the time spent
running functions in that library are also recorded.

The contents of that file can be analyzed with the gprof program, to see
where the program spends its time.

Now if you compile a program with not-profiling libraries, gprof cannot
tell you much about the time your program spent in functions in that library.

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. 

I'll be bold and say that modern machines are so fast that there is
seldom need to profile a program.

R.F.Smith (http://www.xs4all.nl/~rsmith/) Please send e-mail as plain text.
public key: http://www.xs4all.nl/~rsmith/pubkey.txt
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