Any drawbacks to changing default makeflags from -j2 to -j4 in system.sh on RPi3?

stoo

Apologies if this is a stupid question:

Are there any drawbacks to changing default makeflags from -j2 to -j4 in system.sh on RPi3 to make builds faster?

mitu

@stoo More compilation jobs means more memory used - which could mean digging into swap and spilling the memory overhead on the card - and full CPU usage. So the drawback will be that the compilation might not be faster and I think you'd need some kind of cooling if you're doing this frequently.
Is there a reason to compile instead of using the binary packages ?

stoo

I'm attempting to modify ScummVM to pseudo-dynamically assign controller buttons based on the connected controller.

Ok, looks like my RPi3 can't handle a 1350mhz CPU clock, even with active cooling. Dropped back to 1300 and the build is progressing fine with -j4.

It was stable at 1350 until I tried -j4, which I guess means it wasn't really stable at all. Good to know.

It certainly seems to be building faster now and memory use is hovering in the 50-60% range and doesn't appear to be hitting swap at all. Obviously that's dependent on what you're building, but if all I have to worry about is memory usage and heat the drawbacks seem minimal.

Thanks, mitu.

zerojay

If something breaks, don't ask for support without trying with -j2 first.

stoo

@zerojay OH NOES I USED -j 9000 AND NOW ALL MY BUILDZ ARE BROKEN HELP PLZ MY PI IS ON FIRE AAAAAHHHH

zerojay

@stoo said in Any drawbacks to changing default makeflags from -j2 to -j4 in system.sh on RPi3?:

@zerojay OH NOES I USED -j 9000 AND NOW ALL MY BUILDZ ARE BROKEN HELP PLZ MY PI IS ON FIRE AAAAAHHHH

Welcome to Gentoo.

stoo

@zerojay lol, here's a pointless story:

About 12 years ago I was just messing around, trying to build Gentoo on a (very) old Acer laptop. Well, something went wrong and the build froze. These laptops had an actual pot wheel type volume control on the side, and apparently the Acer engineers hadn't thought "hey, how about some actual circuitry that sets a sane limit on the volume?"

The volume control was set to maximum and the build failing caused a continuous tone from PC beeper, which was amplified through the built-in speakers . People in surrounding offices actually started evacuating because they thought it was the fire alarm. Yes, it was that loud.

(I just realised that evacuating can have two meanings, both of which are valid in this case.)