Re: Suggestions for improving gcc 3.2 compilation speed?

[Anna Fowles-Winkler <awinkler at maad dot com>]

Joel Sherrill wrote:

> "Kaveh R. Ghazi" wrote:
>  
>
> > > I've been running gcc 2.95.3 on a 1Ghz/512MB RAM PC running RedHat
> > > 7.2. It takes 20 minutes to compile my application, so I recently got
> > > a new computer to reduce the time I wait for compiles. This new
> > > computer is a 2.8 Ghz CPU/1GB RAM running RedHat 8.0. Since RedHat 8.0
> > > comes with gcc 3.2 I figured I'd give it a try. It takes 20 minutes to
> > > compile my application. (!!!)
> > >
> > > I'm a little frustrated that the compilation speed is so slow with gcc
> > > 3.2, especially since this is a commercial application (i.e., this is
> > > my job). Is there anything I can do to improve the compilation speed?
> > > Will newer gcc releases be as fast as gcc 2.95.3 (or faster)? Or is my
> > > best bet to stick with 2.95.3?
> >
> > With 1GB of RAM, try this patch it might help some.  But on machines
> > with less memory it may cause thrashing, so it's not a general
> > solution.
> >    
>
> Have you tried using some parallelism in your build?  I work on an 
> application with 425K lines of mostly C++ which we build for two 
> target OSes.  It takes about 20 minutes on a 2.4 Ghz dual Xeon
> with 2 GB RAM.  We added a -j option to make and the build time 
> dropped to a little under 8 minutes.  The parallel make keeps the
> CPU busy while the OS is accessing the disk to read source files
> and write objects.  The difference in CPU utilization is incredible.
> The non-parallel make only hit about 25% CPU utiliization.  The
> parallel version stays close to 100% for most of the build.
>  
Good thought.  I tried it this morning:  both compiles (with and without 
the -j make option) take 18 minutes (more officially timed then my 
glance at the clock timing).

--Anna