rtems-bsp-builder Job Load Calculation

[Chris Johns]

On 2020-04-04 07:57, Joel Sherrill wrote:
> How does rtems-bsp-builder calculate the amount of parallelism to use?

The option is documented here ...

https://docs.rtems.org/branches/master/user/tools/bsp-builder.html#cmdoption-jobs

and is ...

  --jobs

  The jobs options where the format is build-jobs/make-jobs. The default
  is 1/num-cores where num-cores is the operating system reported number
  of cores.

> I ask because I have realized that I selected jobs=6/12 on a very beefy 
> machine with 12 cores and 32 GB RAM. The main test machine I use is 8 
> cores/32 GB RAM. But the slowest ones are old with 4 cores/4 GB RAM. 
> They are hitting the swap space. All have SSDs.
> 
> Should I drop the --jobs parameter? Will the script select a decent load 
> automatically? The machines are essentially dedicated to testing.

You will need a --jobs option or the machine will not be fully loaded. 
You need to find a balance between the number of parallel BSPs that are 
built at once and the number of parallel build jobs each BSP makes runs.

The critical factor is the amount of bootstrap and configure time. This 
is a single core task and if you use the default a lot of the build time 
the machine is basically idle.

There is no way I know of to automatically find this balance for all the 
different types of host machines.

Chris