Default Kernel Updates

naim · October 10, 2024, 5:16am

Hello CachyOS Enthusiasts

Following the 6.11.2 kernel, our default kernel linux-cachyos is now compiled with clang+ThinLTO by default. This means that the linux-cachyos-lto kernel is now obsolete and systems with that package installed will be replaced with the linux-cachyos package. We have also added a linux-cachyos-gcc package that is the default kernel built with GCC (the default before 6.11.2) for legacy reasons and a possible fallback kernel.

Users can expect a slight bump in performance, mainly in micro-benchmarks from this change. [Phoronix Benchmark].

P.S. The rc kernel linux-cachyos-rc also defaults to ThinLTO now. This means that a linux-cachyos-rc-gcc kernel also exists.

For more information, please see the links below and report any issues you might have come across due to this change. Thank you as always!

github.com/CachyOS/linux-cachyos

[RFC] Using Clang (ThinLTO) for the default kernel in the cachyos repository

opened 04:33PM - 29 Aug 24 UTC

closed 07:15PM - 05 Oct 24 UTC

ptr1337

enhancement

Hi, Im considering to use the ThinLTO for the "linux-cachyos" as default in t…he cachyos repository. Clang built kernel has been pretty stabilized over the years and is also used by Google in Android as default, together with ThinLTO. ## The Clang built Kernel provides as a bunch of benefits, like: - Rust support (could be interesting for using https://www.phoronix.com/news/Linux-6.12-DRM-Panic-QR-Code) - Better Performance --> https://www.phoronix.com/review/clang-lto-kernel ## There are some outstanding issues, which needs to be discussed/fixed: - ~~nvidia-open-dkms with ThinLTO does not boot, fix can be found here: https://github.com/dell/dkms/pull/417~~ https://github.com/CachyOS/CachyOS-PKGBUILDS/commit/f4020405499a3b0bf5676e9f3994fc3b40c007a8 - ~~Find other dkms modules, which are not compatible~~ - The maintenance of the archlinux clang toolchain - ~~Test kCFI/FineIBT for the kernel and its impact on performance and modules~~ - Breaks NVIDIA modules This issue is for general discussions and fiddling out the pending issue, which needs to be resolved. Also, we should consider providing the default kernel built with GCC too, with a "linux-cachyos-gcc" variant or equal, but this will be only used for the cachyos repository. ## known problematic DKMS Modules: - ~~vmware-workstation~~n (Maybe we can put this at compilation time, like we do with zfs/nvidia) https://paste.soulharsh007.dev/p/5tY8t6.log - workaround available here: https://github.com/CachyOS/CachyOS-PKGBUILDS/pull/320 can not be distributed, due license - ~~nvidia-390xx-dkms~~ Fixed by: https://github.com/CachyOS/CachyOS-PKGBUILDS/pull/318 - ~~nvidia-470xx-dkms~~ Fixed by: https://github.com/CachyOS/CachyOS-PKGBUILDS/pull/319 - 8192cu-dkms - https://paste.cachyos.org/p/6059efb.c - rtl8812au-dkms - https://paste.cachyos.org/p/385e3f2.txt - rtl8821cu-morrownr-dkms-git - https://paste.cachyos.org/p/7545b73.txt - ~~rtl88xxau-aircrack-dkms-git - https://paste.cachyos.org/p/2fe7c0c.log~~ - mainly ARM project, ignoring. ## Benchmarking We should benchmark the ThinLTO kernel compared to the GCC quite much. There will be a bunch of cachyos-benchmarker tests done, as well as a bigger phoronix test suite. Aditionally we should test using different marches, e.g v3/znver4 if there are any regressions found

github.com/CachyOS/linux-cachyos

linux-cachyos: Default to ThinLTO

CachyOS:master ← CachyOS:default-thinlto

opened 12:59AM - 01 Oct 24 UTC

1Naim

+85 -13

Second and final part of #286. The default kernel will now use clang + ThinLTO a…s its default configuration. To accomodate this change, I have added a conditional statement for each `_package` function to replace existing LTO kernels that are already installed to smoothen the transition. Furthermore, I have modified the build script to ensure that all PKGBUILDs will build with GCC first before building the LTO kernels. We should do a staged rollout for this change to cachyos-testing-v3 -> cachyos-znver4 -> all repos to ensure that everything works correctly (most notably dkms modules, even though they compile successfully, we should ensure complete functionality) Closes #286

altman · October 10, 2024, 9:35am

Thx for the hard work here @naim & the Team.

Mwa · October 10, 2024, 2:03pm

I wonder if thinLTO is much better then BORE

Jeoshua · October 10, 2024, 2:16pm

Those aren’t the same kind of thing.

ThinLTO is a way of optimizing a program during the linking process. I’m not 100% on exactly how it works, but it has something to do with laying out things in a more optimal way in the final executable, itself.

BORE is a scheduler, which controls how code is run, which threads are given priority, how tasks switch off control of the cpu, etc.

You can use both at the same time. It’s like having a car which is both a sedan and has a turbo in it.

Mwa · October 10, 2024, 2:41pm

ohhhh i thought it was a scheduler replacement

altman · October 10, 2024, 3:06pm

❯ pacman -Qi linux-cachyos                                                                                                                    ─╯
Installed From  : cachyos-v3
Name            : linux-cachyos
Version         : 6.11.2-5
Description     : The Linux SCHED-EXT + BORE + Cachy Sauce Kernel by CachyOS with other patches and improvements kernel and modules
Architecture    : x86_64_v3
URL             : https://github.com/CachyOS/linux-cachyos
Licenses        : GPL-2.0-only
Groups          : None
Provides        : VIRTUALBOX-GUEST-MODULES  WIREGUARD-MODULE  KSMBD-MODULE  UKSMD-BUILTIN  linux-cachyos-lto=6.11.2-5
Depends On      : coreutils  kmod  initramfs  scx-scheds
Optional Deps   : wireless-regdb: to set the correct wireless channels of your country
                  linux-firmware: firmware images needed for some devices [installed]
                  modprobed-db: Keeps track of EVERY kernel module that has ever been probed - useful for those of us who make localmodconfig
                  uksmd: Userspace KSM helper daemon
Required By     : linux-cachyos-headers  linux-cachyos-nvidia
Optional For    : None
Conflicts With  : None
Replaces        : linux-cachyos-lto
Installed Size  : 139.32 MiB
Packager        : CachyOS <admin@cachyos.org>
Build Date      : Sun 06 Oct 2024 12:54:09 PM EDT
Install Date    : Wed 09 Oct 2024 05:19:44 AM EDT
Install Reason  : Explicitly installed
Install Script  : No
Validated By    : Signature

iSpeakVeryWell · October 10, 2024, 11:26pm

Thanks guys! Good work!