Neal Murphy neal.p.murphy at alum.wpi.edu
Fri Mar 25 14:58:28 PDT 2011

On Friday 25 March 2011 17:39:02 Mike McCarty wrote:
> Neal Murphy wrote:
> > On Tuesday 22 March 2011 17:10:52 Mike McCarty wrote:
> >> Why do you say that? IME, most of the time is spent in the
> >> compiler, not reading the CD-ROM. It takes a few seconds to
> >> read the CD-ROM to get the compiler going, and then it runs.
> >> Usually, most of it gets cached.
> > 
> > Only if you have enough RAM. Taking a SWAG, 2GB ought to be enough to
> > cache
> Even much less. If there is enough RAM to hold the compiler, it
> takes a few seconds to load it up, and then it runs from memory.
> I've built from LiveCD with 512MB of RAM, and most of the time
> was waiting on the processor, not the disc.

It's not just the compiler, but also the linker, the libraries, make, shell, 
utilities, etc. Now add in the object files being linked and the libraries 
being linked to and yer startin' to talk about real memory. Linux itself 
balloons from around 120MiB unpacked to 900GiB or so built. So I'll compromise 
and say it depends on what you are building. :)

Another number to add that highlights Linux's caching. When building, my %wa 
(waiting for IO) rarely climbs above 0.3 and is most often 0.1 or less. Then 
when I rebuild, there's no waiting for input, and rarely waiting for output.


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