bugmake - Bugs: bug #49844, 'make -j' without explicit process...


bug #49844: 'make -j' without explicit process count sometimes doesn't parallelize

Submitted by:  Dima Kogan <dkogan>
Submitted on:  Wed Dec 14 19:02:15 2016  
Severity: 3 - NormalItem Group: None
Status: NonePrivacy: Public
Assigned to: NoneOpen/Closed: Open
Component Version: NoneOperating System: None
Fixed Release: NoneTriage Status: None

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Wed Dec 14 19:02:15 2016, original submission:

Hi. I have this trivial Makefile:

echo Starting $@ || true
timeout 5 bash -c 'while true; do true; done' || true
echo Done $@ || true

It's meant to spin the cpu for 5 seconds for each target being built. I can ask for 5 simultaneous jobs with something like 'seq 1000 | xargs -n1000 make -j5' and this command should always redline 5 CPUs. If I give 'make -j' instead of 'make -j5' I would expect it to redline ALL my CPUs, but I see it not do any parallelization at all instead. If the Makefile contains normal (not pattern) rules, then it works how I would expect.

Dima Kogan <dkogan>


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