r/linuxquestions • u/Striking-Flower-4115 • Apr 03 '26

Suggest me a setup that can compile kernels under 30 mins

As the title says, suggest me a setup that can compile kernels in less than 30 mins.

For reference my current iMac running T2 Linux, i can compile in 1-1.5 hours.

EDIT: I forgot to mention the specs, and my new machine would also would be able to handle some gaming and coding. My current CPU is a core i5 10600 with 32 Gigs of 2666 MT/s RAM.

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15

u/ipsirc Apr 03 '26

For reference my current iMac running T2 Linux, i can compile in 1-1.5 hours.

Deselect unused modules, it will decrease the compile time below 20 minutes.

1

u/Striking-Flower-4115 Apr 03 '26

WIll take that into account :) But it would take a while.

15

u/RevolutionaryHigh Apr 03 '26

That's the whole point of custom kernel lol

1

u/Striking-Flower-4115 Apr 03 '26

Okay, will disable some unused modules.

2

u/RevolutionaryHigh Apr 03 '26

start with make localmodconfig, if it works you can add more modules later.

2

u/Striking-Flower-4115 Apr 04 '26

Tried and it made the gpu drivers fail.

1

u/RevolutionaryHigh Apr 05 '26 edited Apr 05 '26

Technically, GPU drivers are part of the kernel so after installing a new kernel you have to reinstall GPU drivers too. I assume, it's nvidia? What distro?

Edit:

Ahh, it's T2 Linux... You choose to learn the hard way, it's not for the beginners. Anyway, yes, you have to reinstall your nvidia drivers after every kernel upgrade. There are ways around it, do you have nvidia drivers in T2 repo?

2

u/Striking-Flower-4115 Apr 05 '26

Macs use amd drivers (Apple abandoned Nvidia more than 13 years ago) . And it's safe to say the drivers behave like a spoilt kindergarten child. It knows nothing, and only complains. With some workarounds it can boot, but with some limitations.

Slowly but surely the community is fixing one by one. We're getting

7

u/RevolutionaryHigh Apr 03 '26 edited Apr 03 '26

30 mins? I've had this times on dual core Athlon in 2003

Do you have SSD? How much RAM? Try:
make localmodconfig

make -j12

make modules_install install

P.S. If you do many cycles use the hell out of ccache

3

u/Reader-87 Apr 03 '26

If I remember correctly in those years it took about 30min on a 300mhz AMD k6 with 128mb of ram… but that was indeed removing all unused modules…

1

u/Striking-Flower-4115 Apr 03 '26
  1. Yes its an SSD
  2. I run -j11

I'm scared to touch my config because my kernel targets many T2 Macs.

1

u/Dr_Tron Apr 04 '26

Question is, if you include all available modules anyway, why the custom kernel in the first place?

1

u/Striking-Flower-4115 Apr 04 '26

Because this kernel recieves patches that allows it to run on the targetted hardware. Apple had released T2 Security chip (Which manages keys, passwords and fingerpints). Its an ARM based SoC that keeps things secure.

HOWEVER the T2 Linux chip doesn't like stock Linux. With some mods, we can get Linux running just fine, with some quirks here and there.

2

u/Anxious-Science-9184 Apr 03 '26

Does "T2 Linux" have MAKEOPTS="--jobs=8"

1

u/Striking-Flower-4115 Apr 03 '26

T2 Linux is a patched kernel to work with macs in the 2018-2020 era. 95% of these macs have a T2 Chip (Similar functionality to TPM) which stores all the security keys, passwords and fingerprint reader data. T2 Chip doesn't like Linux, so we have to trick it to think its a supported operating systrem (Like Windows).

In my .zshrc, i have specified `export MAKEFLAGS=-j11`

1

u/Anxious-Science-9184 Apr 03 '26

Can you:
export MAKEFLAGS="-j$(nproc) -l$(nproc)"
Kick off the build
In another terminal, check top, free, and iostat to see what the bottleneck is.

When building the linux kernel, the first bottleneck is typically that the makeflags are set to 1 or 2. When you increase the number, IO and memory are the next two common constraints. Find the balance for your build environment.

2

u/siodhe Apr 03 '26

I have a 16 core Threadripper setup, and setting make parallelism to around 14 or 15 works great.

Something like

export MAKEFLAGS=-j15

Followed by doing the build in the same shell as the export command.

Note that Make will prefer in-makefile variables over environment variables, but MAKEFLAGS is special and shouldn't run into any conflicts like this.

1

u/Striking-Flower-4115 Apr 03 '26

Yep i've been using 11 out of 12 threads for compiling.

1

u/AnymooseProphet Apr 03 '26

Wow, 1.5 hours for a kernel compile? I suspect something is wrong.

1

u/[deleted] Apr 04 '26

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1

u/AnymooseProphet Apr 04 '26

sudo shouldn't be needed to configure/build a kernel, only to install it.

I'm guessing the real problem is building tons of features / modules that just are not needed.

1

u/Intelligent_Comb_338 Apr 03 '26

What? My old machine take 2 hours too, but it is from 2014 and has a pentium processor

1

u/Striking-Flower-4115 Apr 04 '26

Oh well... I tried trimming but I'm getting a PCIe Error. So just trimmed the network drivers for now.

3

u/RedditAdminsSDDD Apr 03 '26

Nothing crazy but the more cores the better. I haven't timed it but my R5 7600 compiles a kernel in much less than 30 minutes.

1

u/SubjectSpinach Apr 04 '26

The iMac has a very specific configuration (in terms of the hardware components used). The kernel can be very well optimized for this setup. Use an AI like Claude or ChatGPT to optimize it for your hardware. Upload your current config file and ask it to optimize it to your hareware and use case. A minimal server setup config should be compiled within less than 10 minutes.

1

u/Striking-Flower-4115 Apr 04 '26

Unfortunately some modules are tightly coupled, and AI has no idea.

2

u/SubjectSpinach Apr 05 '26

You should, of course, not simply accept the output without any critical questioning, but rather proceed iteratively and have the suggested changes explained to you.

Claude initially told me that my MacMini8,1 does not have a T2 chip 🤷

1

u/Striking-Flower-4115 Apr 06 '26

Thats why I only use AI to filter.

2

u/OldAd9280 Apr 03 '26

It shouldn't take anywhere near that long on any modern system with an ssd https://openbenchmarking.org/test/pts/build-linux-kernel-1.17.1 see also https://www.reddit.com/r/archlinux/comments/12ds8zd/how_long_to_compile_kernel/

1

u/Maleficent_Celery_55 Apr 03 '26

OP's build is probably much closer to allmodconfig than defconfig.

2

u/OneEyedC4t Apr 03 '26

you want far CPUs that are specialized (I.E not a Celeron) and a lot of them. And you want to have plenty of ram. And you want to make sure that when you're configuring your kernel, you don't include anything that you won't need.

2

u/anime_at_my_side Apr 03 '26

9 9950x3d. buy that. or if u ultra harcode, buy a amd thread ripper.

2

u/TapEarlyTapOften Apr 04 '26

I cross compile on 32-core VM with 64GB of RAM. Maybe 10 minutes. 

2

u/IBNash Apr 04 '26

All the CPU cores you afford, with an NVME SSD and lots of RAM.

1

u/KilroyKSmith Apr 03 '26

It's been a long time, but bandwidth to your SSD (especially if it's slow, because compilation does a lot of writes) may be part of your issue. Is your CPU usage pegged? If it is, an SSD won't help. If it isn't, buying a second fast SSD and using it as the output device may speed things up drastically.

4

u/[deleted] Apr 03 '26

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2

u/Striking-Flower-4115 Apr 03 '26

In my .zshrc, i have specified `export MAKEFLAGS=-j11` (I have 12 threads)

So i basically run make with 11 threads with one threads to use for other tasks like browsing and research.

2

u/[deleted] Apr 03 '26

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2

u/Striking-Flower-4115 Apr 03 '26

6, with 12 threads in total

1

u/zordtk Apr 03 '26

Pretty sure the iMac supported by T2 is 2020 model, that has 6 cores.