I have a small problem related to kernel build time. Sorry for a bit messy writing. I'm very poor at it. :D We (my team) are using qemu for rebuilding Linux kernel for our product. We all share similar hardware - more or less at least (details described later). What's very interesting, the compilation time can differ dramatically between our hosts. We talk about differences between 3-5min till an hour.
Measured after make clean. All of us build it using qemu-arm emulating bash on mounted image of the whole system(system of the device we develop). the system itself doesn't run. Just chroot+emulated arm bash that runs other arm programs and calls kernel of the host. For two of three hosts all of this is additionally encapsulated inside of a full Linux (Ubuntu VM) because they run Windows on hosts. All hosts make use of all available cores.
Timings of full rebuild and description of hardware-software used:
- host 1. Win + Hyper-V emulating Ubuntu 20(kernel 5.4.3). I7 8th gen 6 cores. 16GB ram. 8 for VM Time 3m50s.
- host 2. Win + VMBox (hardware virtualization) Ubuntu 18(kernel unknown but rather 5+). I7 9th 6 cores. Time around 30 mins. 6GB ram for VM.
- host 3. Linux (manjaro). Kernel 5.8. I7 6th 4 cores. 40GB ram. qemu runned on host without Ubuntu VM. Time is about an hour.
Hardware is a bit different but not different enough to generate such differences. Processors are more or less the same. 9th gen goes much worse than 8th. 6th is out of scale. Hardware based(accelerated) virtualization shall not be a problem since host without it makes the worst.(maybe something is different between Linux and Windows? But it doesnt make much sense because at the end of the day it's being build on Linux. Arch/Debian doesn't make difference i guess). Ram shall also not be significant as long as minimum is reached. I think it is in every case.
I write because none of those data makes sense. I was also trying to find what can affect the build time in such configuration but as you see it's quite specific - didn't have much success.
Do you have any idea what specs/settings could also influence the build?
Thanks for your attention,time and bearing my writing style ;-)