Re: Settings for parallel make jobs not applied

On 29/09/2022 12:04, "md" ([email protected] via alfs-discuss 
Mailing List) wrote:
> I'm having problems with switching on 2 parallel make jobs.
> Assuming this problem is resolved, is it still a valid recommendation to
> exclude gcc from the parallel builds?
> It's the package that takes most time to build.
>
> Section 5. RUNNING ofhttps://wiki.linuxfromscratch.org/alfs/browser/README
> mentions
> that using "Optimization and parallelisation" "you'll be able to select the
> number of parallel `make'  jobs".
> Also the lfs book mentions export MAKEFLAGS='-j4'
> https://www.linuxfromscratch.org/lfs/view/systemd/chapter04/aboutsbus.html,
> but it's not clear whethet this is supported by jhalfs, even if MAKEFLAGS
> appears in the jhalfs source.
>
> Here is how I'm trying to configure make to use two jobs.
> After enabling "Optimization Settings" in "make", the "jhalfs run" shows the
> following, relevant output

I'm just user of jhalfs so I can only share my own experience:

export MAKEFLAGS='-j4' is just one example on how to implement 
MAKEFLAGS! Exact implementation depends on your situation.
jhalfs does not use this variable but implements it's own with default 
value 1. Some packages do not support parallel build and request make 
j1. For my (in VM with 16 cores) works good with Optimizations number 
set to 16 because the VM is dedicated to one task: building LFS. 
Remaining 8 cores are used by host.
You should never number of MAKEFLAGS="-jn" or Optimizations higher than 
number of cores on your system.
If you are using machine also for other tasks than building LFS you can 
start by optimization set to 1/2 of cores and based on gained experience

As far I know documentation of jhalfs is way out of time and decidedly 
on that point.
In my experience if jhalfs build breaks than by restart retries to build 
from the same package where it stopped. I've not experimented to break 
build up, change optimization settings and restart build.
I do not know what would happen.
I do believe that setting Optimizations higher will not cause any problems.

PS: Is that the your first attempt to build LFS system? In that case I 
will strongly advice you: DO NOT proceed and build LFS by the "hand" to 
gain experience.
I started to use jhalfs after first building few versions of LFS by the 
hand and pass then started using jhalfs.

Dragan

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