I get that the OS could mitigate this, but that’s often not an option in professional settings. The reality is that most of the time users are expecting ‘make -j $(N_PROC)’, get bit in the ass, and then the GNU maintainers say PEBKAC—wasting hundreds of hours of junior dev time.
I would put that in the “using it improperly” category. I never use⁰ --jobs without specifying a limit.
Perhaps there should have been a much more cautious default instead of the default being ∞, maybe something like four¹, or even just 2, and if people wanted infinite they could just specify something big enough to encompass all the tasks that could possibly run in the current process. Or perhaps --load-average should have defaulted to something like min(2, CPUs×2) when --jobs was in effect⁴.
The biggest bottleneck hit when using --jobs back then wasn't RAM or CPU though, it was random IO on traditional high-latency drives. A couple of parallel jobs could make much better use of even a single single-core CPU, by the CPU-crunching of a CPU-busy task or two and the IO of other tasks ending up parallel, but too many concurrent tasks would result in an IO flood that could practically stall the affected drives for a time, putting the CPU back into a state of waiting ages for IO (probably longer than it would be without multiple jobs running) - this would throttle a machine² before it ran out of RAM even with the small RAM we had back then compared to today. With modern IO and core counts, I can imagine RAM being the bigger issue now.
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[0] Well, used, I've not touched make for quite some time
[1] Back when I last used make much at all small USB sticks and SD cards were not uncommon, but SSDs big++quick+hardy enough for system or work drives were an expensive dream. With frisby-based drives I found a four job limit was often a good compromise, approaching but not hitting significantly diminishing returns if you had sufficient otherwise unused RAM, while keeping a near-zero chance of effectively completely stalling the machine due to a flood of random IO.
[2] Or every machine… I remember some fool³ bogging down the shared file server of most of the department with a vast parallel job, ignoring the standing request to run large jobs on local filesystems where possible anyway.
[3] Not me, I learned the lesson by DoSing my home PC!
[4] Though in the case of causing an IO storm on a remote filesystem, a load-average limit might be much less effective.
Personally, I don’t think these footguns need to exist.
They are junior because they are inexperienced, but being junior is the best place to make mistakes and learn good habits.
If somebody asks what is the most important thing I have learnt over the years, I’d say “read the manual and the logs”.
Make does not provide a sane way to run in parallel. You shouldn’t have to compose a command that parses /proc/cpuinfo to get the desired behavior of “fully utilize my system please”. This is not a detail that is particularly relevant to conditional compilation/dependency trees.
This feels like it’s straight out of the Unix Haters Handbook.
[0]: https://web.mit.edu/~simsong/www/ugh.pdf see p186
However, if "make -j" is saturates a machine, and this is unintentional, I'd assume PEBKAC, or "holding it wrong", in general.