perhaps you should look at how ceph has dealt with a similar issue,
they set the max number of cpus based on the system ram.
https://src.fedoraproject.org/rpms/ceph/blob/rawhide/f/ceph.spec#_1246

Dennis

On Fri, Mar 26, 2021 at 7:49 PM Michel Alexandre Salim
<mic...@michel-slm.name> wrote:
>
> Hi all,
>
> This idea came about when I'm debugging build issues with mcrouter,
> which turns out to be due to build jobs failing to allocate memory and
> getting terminated without aborting the entire compilation, causing
> link issues when empty or corrupted objects are encountered:
>
> https://src.fedoraproject.org/rpms/mcrouter/blob/rawhide/f/mcrouter.spec#_4-8
>
> As a rough estimate it seems like each of the CPU core passed with
> %{_smp_build_ncpus} ended up consuming close to 8 GB of RAM. And that's
> with LTO disabled (yeah, it's not a good situation to be in).
>
> Right now I'm just overriding _smp_build_ncpus to 1, but there is a
> more elegant solution I'd like to propose:
>
> What if one can declaratively set the required RAM per build job --
> either with a single macro, or maybe two if the LTO usecase requires
> even more RAM. e.g. to declare each core might take up to 8 GB:
>
> %global _smp_build_ram_per_cpu 8192
>
> then in case this is run on our aarch64 builder with 40GB RAM,
> dynamically take the minimum of the existing _smp_build_ncpus (which
> AIUI is determined by the number of cores on the machine) and (amount
> of RAM / _smp_build_ram_per_cpu), in this case capping the actual
> number passed to -j to 5.
>
> Is there interest in having this be available? I could imagine it might
> be useful for other resource-intensive package builds e.g. for
> Chromium.
>
> Best regards,
>
> --
> Michel Alexandre Salim
> profile: https://keyoxide.org/mic...@michel-slm.name
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