[Scons-users] Not able to make full use of CPUs for processing speed

[Don Baldwin]

Hi,

We have a build machine with, say, N CPUs, and we try increasing num_jobs to a higher value, but we're not seeing a decrease in build times.

For example, say we have 10 CPUs.  We would expect that as num_jobs approaches 10, we would continue to see better and better performance during the compile phase.  However, what we're seeing is that performance improves until num_jobs hits about 5, at which point further increases to num_jobs isn't having an effect.

My suspicion is that SCons is doing a lot of processing on it's own trying to figure out which jobs to queue next, e.g. scanning .c files for new implicit dependencies, and that there's a theoretical limit on how many CPUs it's able to keep up with.  Could something like that be going on?

Thanks,
Don
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