Re: make doc problem

[Phil Holmes]

"Julien Rioux" <address@hidden> wrote in message 
news:address@hidden
> On 22/01/2012 2:38 PM, David Kastrup wrote:
> > Julien Rioux<address@hidden>  writes:
> >
> > > I can't run -j, I have a single core.
> >
> > This is factually incorrect.  You can run -j just fine, but you can't
> > expect much of a speedup.  On a single-core machine,
> >
> > make -j 2
> >
> > typically gives you a speedup of maybe 15% (given sufficient memory)
> > since the CPU can keep busy on processing a second job when the other
> > job is waiting for the disk to provide new input.
> >
> > More importantly, you'll get to see the same kind of problems that the
> > true multi-core people experience when using -j.
> >
> > So very much recommended for testing.
>
> Thanks, you're quite right CPU is not the limiting factor for the build. 
> Disk access and usage of swap when compiling 
> input/regression/collated-files slows down the build to a crawl for me.
>
> --
> Julien

As a general rule, CPU is very much the limiting factor on make and make 
doc.  With my "single cpu" virtual machine on my Windows box, the CPU is 
stuck at 100%.  With my multi-core Ubuntu box, most of the time all 8 CPUs 
run 100%, with memory never over 1.5 Gigs.  This is using a fairly large 
SSD, but I'm 99% certain that, all other things being equal, CPU is king 
when building lily.

--
Phil Holmes
Bug Squad