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Ant P.
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Joined: 18 Apr 2009
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 Posted: Fri Feb 28, 2020 7:08 pm Post subject: |
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| That's a good point. I let `make install` manage /boot/vmlinuz and vmlinuz.old but I keep a third boot entry that's only updated by hand. It's saved me from needing a USB stick a few times now. |
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figueroa
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Joined: 14 Aug 2005
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| Posted: Fri Feb 28, 2020 8:11 pm Post subject: |
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| Ant P. wrote: | | figueroa wrote: | | Ant P. wrote: | | `make oldconfig` takes literally 20 seconds and an incremental build takes minutes, not hours. |
I've been using `make olddefconfig` for the last year or so. Do you believe that's a sound practice? |
It's mostly a matter of preference. I prefer to audit the new options because there's still the occasional default-Y hardware driver sneaking in, and sometimes an interesting thing appears like SENSORS_DRIVETEMP that I'd miss otherwise.
Either way, there's scripts/diffconfig that can show you exactly what you agreed to. |
Thanks those reasons and hints. I guess I need to audit my current .config.
I got the idea of changing to use olddefconfig from the Gentoo Kernel Upgrade Wiki at https://wiki.gentoo.org/wiki/Kernel/Upgrade that doesn't even mention using `make oldconfig` 
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hp pavilion hpe h8-1260t/2AB5; spinning rust x3
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Jaglover
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Section_8
l33t
Joined: 22 May 2004
Posts: 627
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| Posted: Fri Feb 28, 2020 11:04 pm Post subject: |
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| erm67 wrote: |
I don't think those are updated anymore:
RIP pappy:
https://forums.gentoo.org/viewtopic-t-1108804.html
The idea was good however, since everybody wants a different kernel, the only way is to start with a generic and apply to it what you need. You don't certainly want systemd options in your kernel ..... |
So sorry - I lurk here a lot, but missed that post that Pappy passed away. He contributed a lot to Gentoo. |
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Hu
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Posts: 21714
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| Posted: Sat Feb 29, 2020 1:46 am Post subject: |
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| Tuning a kernel to its intended use can be helpful for several reasons. Omitting unnecessary code means less attack surface. It reduces kernel memory usage, which means more memory is available for the system to do useful work. (On non-embedded systems, the percentage savings here is probably not enough to be interesting, though.) It reduces kernel build time, by not building functionality you won't be using. It may improve kernel startup performance by not initializing drivers which then find no hardware to manage. |
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figueroa
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Joined: 14 Aug 2005
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Location: Edge of marsh USA
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| Posted: Sat Feb 29, 2020 3:13 am Post subject: |
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| Ant P. wrote: | | It's mostly a matter of preference. I prefer to audit the new options because there's still the occasional default-Y hardware driver sneaking in, and sometimes an interesting thing appears like SENSORS_DRIVETEMP that I'd miss otherwise. |
Re: make olddefconfig vs make oldconfig
Of course, I didn't say it, but I'm still using 4.9 series (currently at 4.9.210 stable), so I'm not expecting biggie new features. But, I think I'll change my slovenly lazy habits and go back to oldconfig.
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hp pavilion hpe h8-1260t/2AB5; spinning rust x3
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C1REX
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Joined: 02 Jan 2004
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| Posted: Sat Feb 29, 2020 11:46 am Post subject: |
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Hu - thanks for yet another good argument :)
So to summarise if config is done right then compiling may:
- reduce boot time
- reduce compilation time
- less or even 0 module mess
- less security holes
- little bit less Ram usage what might help old hardware
- potentially performance boost if genkernel is missing some options
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erm67
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Joined: 01 Nov 2005
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Location: EU
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| Posted: Sat Feb 29, 2020 6:34 pm Post subject: |
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| C1REX wrote: |
- potentially performance boost if genkernel is missing some options |
Only in the unlikely case of a macroscopic error .... don't count on a noticeable boost. And there are no secret patches that boosts performance ......
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Dr.Willy
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Joined: 15 Jul 2007
Posts: 547
Location: NRW, Germany
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| Posted: Wed Mar 04, 2020 7:50 pm Post subject: |
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| figueroa wrote: | | I used to use https://kmuto.jp/debian/hcl/ to help me with hardware drivers, but it's been discontinued. Anybody know of a similar resource? |
Sure: /lib/modules/${yourkernel}/modules.alias
It contains a list of all (installed) modules and the hardware it works on as a glob pattern on the hardwares modalias id.
You can find the ids all presently plugged in /sys
| Code: | | find /sys/devices/ -name modalias -exec sort -u {} + |
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Jaglover
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| Posted: Wed Mar 04, 2020 11:48 pm Post subject: |
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| erm67 wrote: | | C1REX wrote: |
- potentially performance boost if genkernel is missing some options |
Only in the unlikely case of a macroscopic error .... don't count on a noticeable boost. And there are no secret patches that boosts performance ...... |
There are no secret options, there are plain options which need to be chosen properly. Genkernel does not do it. As there is not possible to have a generic set of USE flags which satisfies everyone there cannot be generic kernel which is perfect for all use cases.
We have had such threads in past. And we will have them in the future. These are started by people who skip kernel configuration in favor of some generic solution. I guess they do 'make menuconfig', look at all those options and think: aw @#$%, this hurts. And then there is a little voice inside their head, it keeps telling them: you are missing out, you got to do your own kernel. To silence this voice they come here and start a thread like this. Ten people can tell them ten times custom kernel will perform better than generic and they will ignore all these ten, this is not the answer they want to hear. And then when someone comes along and tells them: yea, genkernel is as good as custom then they can happily rest. Unfortunately this is not true, but who cares about truth. Appearances are what count.
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C1REX
l33t
Joined: 02 Jan 2004
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Location: Poland/UK
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| Posted: Thu Mar 05, 2020 12:21 am Post subject: |
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Jaglover - in my case it's the opposite. I ask about genkernel as I've never tried one. Not sure why. It just feels more clean I guess.
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ff11
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Joined: 10 Mar 2014
Posts: 664
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| Posted: Thu Mar 05, 2020 12:43 am Post subject: |
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Well, I use my "sys-kernel/gentoo-sources" with the flags "experimental symlink".
Each update of kernel, I copy my old config in "/etc/kernels/" to the new name-version
After this, genkernel:
| Code: | | # genkernel --menuconfig all |
Update my configuration. Then let the genkernel do the job.
After genkernel, I update my grub and modules:
| Code: | # grub-mkconfig -o /boot/grub/grub.cfg
# emerge -1av @module-rebuild |
And if I need change something on one compiled kernel, I use:
| Code: | | # genkernel --no-clean --no-mrproper --menuconfig all |
I could make a better use of "/etc/genkernel.conf", but at least I know what I'm doing.
I'm happy with genkernel 
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axl
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Joined: 11 Oct 2002
Posts: 1144
Location: Romania
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| Posted: Thu Mar 05, 2020 3:14 am Post subject: |
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When you have one machine, with one kernel... I don't know how much genkernel can help. But when you have like 30... it begins to be very clear.
LIke:
| Code: | find /hosts/ -maxdepth 2 -name config | xargs -i dirname {} | xargs -i echo genkernel --kernel-config={}/config --bootdir={} kernel
genkernel --kernel-config=/hosts/ruja/config --bootdir=/hosts/ruja kernel
genkernel --kernel-config=/hosts/liodiana/config --bootdir=/hosts/liodiana kernel
genkernel --kernel-config=/hosts/sky/config --bootdir=/hosts/sky kernel
genkernel --kernel-config=/hosts/catarina/config --bootdir=/hosts/catarina kernel
genkernel --kernel-config=/hosts/zalina/config --bootdir=/hosts/zalina kernel
genkernel --kernel-config=/hosts/kasandra/config --bootdir=/hosts/kasandra kernel
genkernel --kernel-config=/hosts/dragaia/config --bootdir=/hosts/dragaia kernel
genkernel --kernel-config=/hosts/foiofia/config --bootdir=/hosts/foiofia kernel
genkernel --kernel-config=/hosts/marina/config --bootdir=/hosts/marina kernel
genkernel --kernel-config=/hosts/tiranda/config --bootdir=/hosts/tiranda kernel
genkernel --kernel-config=/hosts/rudeana/config --bootdir=/hosts/rudeana kernel
genkernel --kernel-config=/hosts/ruxanda/config --bootdir=/hosts/ruxanda kernel
genkernel --kernel-config=/hosts/lacargia/config --bootdir=/hosts/lacargia kernel
genkernel --kernel-config=/hosts/aya/config --bootdir=/hosts/aya kernel
genkernel --kernel-config=/hosts/adela/config --bootdir=/hosts/adela kernel
genkernel --kernel-config=/hosts/lemnica/config --bootdir=/hosts/lemnica kernel
genkernel --kernel-config=/hosts/dumernica/config --bootdir=/hosts/dumernica kernel
genkernel --kernel-config=/hosts/todosia/config --bootdir=/hosts/todosia kernel
genkernel --kernel-config=/hosts/cosanzeana/config --bootdir=/hosts/cosanzeana kernel
genkernel --kernel-config=/hosts/self/config --bootdir=/hosts/self kernel |
this is just on a small old server. genkernel is for automating building kernels. it's not for a single kernel. although you could use it for that. But it really shines at building multiple automated builds. |
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krinn
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Joined: 02 May 2003
Posts: 7470
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| Posted: Thu Mar 05, 2020 12:04 pm Post subject: |
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from time to time i do a make oldmodconfig kernel, then look at what new modules are use (it's not magic, simply delegating to eudev the task of telling me what modules are ok for my hardware)
of course it's a pain, it takes lot of time building all these modules, but if you ever do it, you'll be surprise by the result |
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C1REX
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Joined: 02 Jan 2004
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Location: Poland/UK
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| Posted: Thu Mar 05, 2020 4:09 pm Post subject: |
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Delete, please :)
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Last edited by C1REX on Thu Mar 05, 2020 7:35 pm; edited 1 time in total |
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figueroa
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Joined: 14 Aug 2005
Posts: 2965
Location: Edge of marsh USA
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| Posted: Thu Mar 05, 2020 5:10 pm Post subject: |
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| krinn wrote: | from time to time i do a make oldmodconfig kernel, then look at what new modules are use (it's not magic, simply delegating to eudev the task of telling me what modules are ok for my hardware)
of course it's a pain, it takes lot of time building all these modules, but if you ever do it, you'll be surprise by the result |
Do you mean "make allmodconfig?" Ref: https://wiki.gentoo.org/wiki/Kernel/Configuration "make help" doesn't show any oldmodconfig.
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hp pavilion hpe h8-1260t/2AB5; spinning rust x3
i7-2600 @ 3.40GHz; 16 gb; Radeon HD 7570
amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi |
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krinn
Watchman
Joined: 02 May 2003
Posts: 7470
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| Posted: Fri Mar 06, 2020 2:48 pm Post subject: |
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| figueroa wrote: | | krinn wrote: | from time to time i do a make oldmodconfig kernel, then look at what new modules are use (it's not magic, simply delegating to eudev the task of telling me what modules are ok for my hardware)
of course it's a pain, it takes lot of time building all these modules, but if you ever do it, you'll be surprise by the result |
Do you mean "make allmodconfig?" Ref: https://wiki.gentoo.org/wiki/Kernel/Configuration "make help" doesn't show any oldmodconfig. |
i mean all not old 
but you guess good from the idea, making everything as modules (except critical to boot ones) then boot that kernel and see what modules are loaded by your dev manager
it is as the debian website you used, but it's more complete (as it work with hwdb list of devices) and it's easier to get the list of modules you should/could have (as you do nothing except an lsmod) |
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5UrNkC27BJ
n00b
Joined: 27 Mar 2022
Posts: 28
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| Posted: Tue Apr 26, 2022 7:02 pm Post subject: Re: What are pros and cons of genkernel? |
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| C1REX wrote: | I've never tried genkernel. Main reason is probably pride and ego.
- Does genkernel use -march=native -O2 flag from make.conf? |
maybe?
i prefer the simple -march=native but i can't find any part of genkernel documentation the any longer supports kernel CFLAGS. just --util-cflags
what i see here is march=core2 and to the best of my knowledge I am exporting HOSTCFLAGS, KERNEL_CFLAGS and hitting a wall with it.
i don't need initrd and have never seen where the contents of initrd are fully maintained and up-to-date.
```
gcc -Wp,-MMD,arch/x86/entry/vdso/.vma.o.d -nostdinc -I./arch/x86/include -I./arch/x86/include/generated -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -fmacro-prefix-map=./= -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -fcf-protection=none -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -march=core2 -mno-red-zone -mcmodel=kernel -DCONFIG_X86_X32_ABI -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -Wno-address-of-packed-member -O2 -fno-allow-store-data-races -Wframe-larger-than=2048 -fstack-protector-strong -Wimplicit-fallthrough=5 -Wno-main -Wno-unused-but-set-variable -Wno-unused-const-variable -fno-stack-clash-protection -pg -mrecord-mcount -mfentry -DCC_USING_FENTRY -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wno-stringop-truncation -Wno-zero-length-bounds -Wno-array-bounds -Wno-stringop-overflow -Wno-restrict -Wno-maybe-uninitialized -Wno-alloc-size-larger-than -fno-strict-overflow -fno-stack-check -fconserve-stack -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wno-packed-not-aligned -DKBUILD_MODFILE='"arch/x86/entry/vdso/vma"' -DKBUILD_BASENAME='"vma"' -DKBUILD_MODNAME='"vma"' -D__KBUILD_MODNAME=kmod_vma -c -o arch/x86/entry/vdso/vma.o arch/x86/entry/vdso/vma.c ; ./tools/objtool/objtool orc generate --no-fp --uaccess arch/x86/entry/vdso/vma.o
``` |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54308
Location: 56N 3W
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| Posted: Tue Apr 26, 2022 7:15 pm Post subject: |
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5UrNkC27BJ,
No part of make.conf is used in the kernel build.
Its just you, the .config file, make and any options you care to pass to make.
Its possible to pass compiler flags to make when you build the kernel but if you do that, you get to keep all the pieces when it breaks.
USE=experimental when you emerge the kernel gets you experimental patch set of the day.
Genkernel itself, when its being built, follows make.conf but i don't think that was the intent of the question,
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Computer users fall into two groups:-
those that do backups
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5UrNkC27BJ
n00b
Joined: 27 Mar 2022
Posts: 28
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| Posted: Wed Apr 27, 2022 9:14 am Post subject: |
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| NeddySeagoon wrote: | 5UrNkC27BJ,
Its possible to pass compiler flags to make when you build the kernel but if you do that, you get to keep all the pieces when it breaks.
|
thanks how, and where is that documented? many years ago kernel CFLAGS was right up front in the GK docs.
i have seen that all of my attempts to be in the env and find switches, short of reading genkernel source, appear to intercept and deleted or string-replaced relating to '-march'.
if is set+export env vars, they do no survive to the makefiles they appear in.
if i set the CC, the -march= gets deleted and the compiler errors everything out.
if i make something clever in makeopts again the variable doesn't translate so well through n levels of escape nesting, and this is clearly a bad idea to bring forward in any write-once-and-forget type of config. and aside from the bad idea part, fails.
for my home-gamer needs, having a localmodconfig setup with RCU i have carried over from vanilla kernels on ubuntu it seems like the best bet is indeed to just inform the build of grub2 and maybe carry along some version string fs-turds to increment. |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54308
Location: 56N 3W
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| Posted: Wed Apr 27, 2022 4:57 pm Post subject: |
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5UrNkC27BJ,
Hint: Read the kernel makefile. Its documented in the comments.
Make sure to practice on a spare kernel, so that the binary and modules are kept separate from your working kernel.
When it breaks, sympathy will be minimal.
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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5UrNkC27BJ
n00b
Joined: 27 Mar 2022
Posts: 28
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| Posted: Thu Apr 28, 2022 4:24 am Post subject: |
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| NeddySeagoon wrote: | 5UrNkC27BJ,
Hint: Read the kernel makefile. Its documented in the comments.
Make sure to practice on a spare kernel, so that the binary and modules are kept separate from your working kernel.
When it breaks, sympathy will be minimal. |
ok so more specifically, how does one use genkernel and not have -march=native squashed as i have seen by abiding linus's makefile? anyone else?
here's what's producing -march=core2 above:
cfg=(
--bootloader=grub2
--no-mrproper
--no-clean
--no-firmware
--no-busybox
--no-keymap
--real-root=UUID=efea9656-2c14-4290-b2c8-0e45b65b6634
--no-zfs
--no-btrfs
--no-virtio
--no-iscsi
--no-ssh
--no-splash
--no-microcode-initramfs
--nice=19
--no-postclear
--compress-initramfs-type=zstd
)
export KERNEL_CFLAGS=' -march=native '
export HOSTCFLAGS=' -march=native '
HOSTCFLAGS=' -march=native ' genkernel all ${cfg[*]} --makeopts='-j8'&& { |
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Juippisi
Developer
Joined: 30 Sep 2005
Posts: 727
Location: /home
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5UrNkC27BJ
n00b
Joined: 27 Mar 2022
Posts: 28
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| Posted: Thu Apr 28, 2022 7:04 pm Post subject: |
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thanks. this patch is in zen, and i used that until the papercuts involved outweighed the efficacy.
sed 's,-march=core2,-march=native,' -i $(find Makefile)
is on my list of simple things to try if i keep with GK, and i really do like GK but for this nit.
'-march' follows all the spelled out -mno flags which presumably come from linus's chosen config switch --march gcc -n choices. (or whatever dumps the arch flags) |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54308
Location: 56N 3W
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| Posted: Thu Apr 28, 2022 7:45 pm Post subject: |
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5UrNkC27BJ,
| Makefile: | # Add user supplied CPPFLAGS, AFLAGS and CFLAGS as the last assignments
KBUILD_CPPFLAGS += $(KCPPFLAGS)
KBUILD_AFLAGS += $(KAFLAGS)
KBUILD_CFLAGS += $(KCFLAGS) |
is the fragment I had in mind.
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NeddySeagoon
Computer users fall into two groups:-
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those that have never had a hard drive fail. |
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