My own experience (pardon me if already discussed)
Fought the build times for several months - ending up eventually at 8 cores (but specifying 16 threads in poky builds). Best times for my build about 4 hours. Clearly impractical during engineering.
Generated an sdk and used it for app development. Each build is now a minute or 2.
Using a homegrown utility, updated the image file with applications in a jiffy - to produce burnable sdcard image.
Complete build required only for the final release -- or made major changes like python2 to python3!
YMMV.
srini
-----Original Message-----
From: yocto@... <mailto:yocto@...> <yocto@...> On Behalf Of Mikko Rapeli via Lists.Yoctoproject.Org
Sent: Wednesday, March 18, 2020 11:52 AM
To: mike.looijmans@... <mailto:mike.looijmans@...>
Cc: yocto@... <mailto:yocto@...>
Subject: <EXT> Re: [yocto] What are the key factors for yocto build speed?
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
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