Re: [yocto] What are the key factors for yocto build speed?

["Mikko Rapeli" <mikko.rapeli@bmw.de>]

On Wed, Mar 18, 2020 at 04:09:39PM +0100, Mike Looijmans wrote:
> On 18-03-2020 15:49, Adrian Bunk via Lists.Yoctoproject.Org wrote:
> > On Wed, Mar 18, 2020 at 10:12:26AM -0400, Jean-Marie Lemetayer wrote:
> > > ...
> > > For example one of our build servers is using:
> > > - AMD Ryzen 9 3900X
> > > ...
> > > - 32Go DDR4 3200 MHZ CL14
> > > ...
> > > It is a really good price / build time ratio configuration.
> > 
> > Depends on what you are building.
> > 
> > Building non-trivial C++ code (e.g. webkitgtk) with 24 cores
> > but only 32 GB RAM will not work, for such code you need
> > more than 2 GB/core.
> 
> Seems a bit excessive to buy hardware just to handle a particular corner
> case. Most of OE/Yocto code is plain C, not even C++.
> 
> My rig only has 8GB but doesn't run into memory issues during big GUI
> builds. The only thing that made it swap was the populate_sdk task that
> created a 1.1GB fiel and needed 20GB of RAM to compress that. Took a few
> minutes more due to swapping.
> I submitted a patch today to fix that in OE.
> 
> Your mileage may vary. But RAM is easy to add.

Well, I can't build with under 2 gigs per core or I run out of physical memory
and kernel oom-killer kicks in to kill the build. Also can't run
with yocto default parallel settings which only take into account the
number of cores and thus have a custom script which does caps the threads
so that 2 gigs of RAM for each are available.

Though I'm sure plain C and plain poky projects have less requirements for RAM.

-Mikko