[oe] PARALLEL_MAKE

[Tom Rini]

On Thu, Mar 12, 2009 at 11:49:30PM -0400, Denys Dmytriyenko wrote:
> On Thu, Mar 12, 2009 at 06:38:54PM -0700, Khem Raj wrote:
> > On Thursday 12 March 2009 16:32:16 Ulf Samuelsson wrote:
> > > Is there any activity to make this more useful?
> > > Just managed to install a Core i7 machine, which speeded
> > > up my Buildroot build from about 4 hours to less than 1 hour.
> > > (There was an error in the build right at the end,
> > > so it could have been downto 40 minutes or so)
> > > Building the cross compiler took 10 minutes with "make -j 16"
> > > compared to 1-2 hours on a P4 @ 3GHz.
> > >
> > > Openembedded does not seem to use PARALLEL_MAKE extensively.
> > > I have the frequency meter activated for all 8 CPUs in the Core i7,
> > > and most of the time the CPUs seems to idle at 1.6 GHz,
> > > with one CPU (or rarely 2) are running at the full 2.67 GHz.
> > >
> > > Last time I built OE on a P4@ 3 GHz it took ~40 hours
> > > for the SAM9263, so some speedup would be nice.
> > > Maybe we should make an effort?
> > 
> > I use 
> > 
> > PARALLEL_MAKE = "-j4" 
> > BB_NUMBER_THREADS = "2"
> > 
> > in my local.conf. I see my core 2 duo machine spawning parallel tasks.
> 
> I'm setting 4/4 to the above two variables on my Quad Core and it loads all 4 
> cores at 100% almost all the time. Sometimes it slows down due to the 
> bottleneck in the harddrive access...

On the dual dual-core (4 total) boxes I have, I do -j6/4 threads.  On my
new quad-core box I haven't yet had a chance to figure out what's best.
I also use -j6/4 threads on an older dual-core amd64 box we've got
around and that seems best for my tasks at least (I tried a few
combinations of more jobs/threads and less and both were slower).

-- 
Tom Rini