Breakage ahead

Posted Jan 21, 2020 19:24 UTC (Tue) by mirabilos (subscriber, #84359)
In reply to: Breakage ahead by josh
Parent article: GNU make 4.3 released

No, the scenario is here to have one (physical or virtual, doesn’t matter) machine with multiple CPU cores, running, for example, two instances of a Debian buildd setup (e.g. one for unstable, one for experimental, or, one for 32-bit and one for 64-bit). The actual builds all happen in isolated chroots (not VMs, so the chroots would “see” all CPUs), but must be limited to nproc/2 (in this scenario).

Another example is building stuff on a workstation while using it (with modern GUI apps that use a lot of CPU) at the same time.

Breakage ahead

Posted Jan 21, 2020 23:48 UTC (Tue) by madscientist (subscriber, #16861) [Link] (1 responses)

You should examine GNU make's -l (lowercase L) option. This works in conjunction with -j by checking the load on the system and ensuring that it doesn't get too high. So, make will start a maximum of -j parallel commands, unless the load is higher than specified with -l.

This is all described in the manual: https://www.gnu.org/software/make/manual/html_node/Parall...

Breakage ahead

Posted Jan 22, 2020 2:00 UTC (Wed) by mirabilos (subscriber, #84359) [Link]

Maybe so, but the process of building Debian packages has a well-defined way for the invoker to specify a maximum number of CPUs to use, so this must be supportable.