Hi,

maybe this function helps:

https://git.ipfire.org/?p=ipfire-2.x.git;a=commitdiff;h=5190eea24f9822a63dc5d06d214b48f973b14f29

On Tue, 2017-11-07 at 10:46 +0000, Michael Tremer wrote:
> On Mon, 2017-11-06 at 22:09 +0100, Matthias Fischer wrote:
> > On 06.11.2017 19:32, Michael Tremer wrote:
> > > Hello,
> > > 
> > > so the big Core Update 115 has been shipped last week. Core Update 116 is
> > > coming
> > > today. So the next one should be a little bit calmer please :)
> > > 
> > > I do not have anything so far except some smaller bug fixes here and
> > > there.
> > > Does
> > > anyone have anything big? It doesn't have to be another big update. We
> > > could
> > > also just improve IPFire where ever it is needed with loads of smaller
> > > changes
> > > and start working on 3 and other sub-projects that are floating around...
> > 
> > I forgot: Tuning the XZ-parameters... ;-)
> 
> Good that you are bringing this up. So I think what we should do here is
> bringing back XZ compression with -8 so that we do not waste too much space
> when
> extracting the image again.
> 
> To not run into memory limits we should detect how much memory the build host
> has and set the memory limit to maybe 80% of that. xz will then automatically
> scale down to a number of parallel processes that it can fit into memory.
> 
> We will at least need about half a GB which should be a sensible requirement
> for
> a build system any ways.
> 
> Will you work on this bringing it into the build system?!
> 
> -Michael
> 
> > 
> > Best,
> > Matthias