[gentoo-user] Testing new kernels - saving dumps / strip down kernel options

[gentoo-user] Testing new kernels - saving dumps / strip down kernel options

[Stefan G. Weichinger]

I recently pulled in the vanilla linux-kernel-sources via git and
compiled my own "daily" kernel to simply test things on my thinkpad.

I get kernel crashes and would like to report them back upstream somewhere.

* to store the crash messages:

Is this still the way to go?

http://wiki.gentoo.org/wiki/Kernel_Crash_Dumps

Any other method recommended?

* should the reports go straight to the lkml-mailinglist?

I feel kind of misplaced there, plain stupid user amongst all those
kernel-devs ;-)

* I remember a thread here where this was discussed already:

How do you guys get to your .config for a recent kernel? "make
oldconfig" doesn't always work out best, I recall?

My kernel config is maintained along for years now and has survived
several hardware changes. I don't have any obvious problems but I wonder
if I have something in there that is deprecated and might be better
thrown out.

Does it make sense to take the .config from the gentoo install dvd for
example and remove all the stuff I don't have? Maybe still too much
enabled options in the end.

"make allnoconfig" as a start?

allmodconfig ?

I'd be happy to hear your opinions.

Stefan

[gentoo-user] Re: Testing new kernels - saving dumps / strip down kernel options

[Nuno J. Silva]

On 2013-01-08, Stefan G. Weichinger wrote:

[...]
> * I remember a thread here where this was discussed already:
>
> How do you guys get to your .config for a recent kernel? "make
> oldconfig" doesn't always work out best, I recall?
>
> My kernel config is maintained along for years now and has survived
> several hardware changes. I don't have any obvious problems but I wonder
> if I have something in there that is deprecated and might be better
> thrown out.

I don't use anything other than stable code releases from portage, but
even then I usually do make oldconfig, followed by a by-hand inspection
of the options with make menuconfig, to catch stuff that got through me
in make oldconfig, and to see if there's any change in other options
that I want to tune.

> Does it make sense to take the .config from the gentoo install dvd for
> example and remove all the stuff I don't have? Maybe still too much
> enabled options in the end.

Even then, if you do that and tune the config several times, you'll
likely end up with a lighter kernel. Just drop anything you don't need
from the device drivers.

> "make allnoconfig" as a start?

That is probably much better than the config from the install dvd, yes,
in fact most of the work coming from an "Add-It-All" config is that you
have to disable many, many entries.

> allmodconfig ?

I'd go with allnoconfig, although if you compile lots of stuff as
modules, you can then check lsmod to see what does, in fact, get loaded.

> I'd be happy to hear your opinions.

-- 
Nuno Silva (aka njsg)
http://njsg.sdf-eu.org/

Re: [gentoo-user] Testing new kernels - saving dumps / strip down kernel options

[Stroller]

On 8 January 2013, at 12:14, Stefan G. Weichinger wrote:
> …
> * I remember a thread here where this was discussed already:
> 
> How do you guys get to your .config for a recent kernel? "make
> oldconfig" doesn't always work out best, I recall?
> 
> My kernel config is maintained along for years now and has survived
> several hardware changes. I don't have any obvious problems but I wonder
> if I have something in there that is deprecated and might be better
> thrown out.
> 
> Does it make sense to take the .config from the gentoo install dvd for
> example and remove all the stuff I don't have?

I most always take the .config from a recent systemrescuecd and it has always worked well for me.

I change "processor type and features" and disable the initrd. 

There may be some stuff on a LiveCD based distro which is optimised for running off an optical disk, so I guess a RedHat or Ubuntu default .config might be better.

These should provide everything you need to boot, and most everything else as modules, which will be automatically loaded. IMO this is pretty much optimal.

The engineers at RedHat and Ubuntu know a heck of a lot more about kernels than I do. One might be able to make one's kernel milliseconds more efficient by tuning it by hand, but it will surely take hours of tinkering to attain that.

I do not believe you can properly understand the consequences of any given kernel option merely by reading the one- or two-line description in makeconfig's help. To *properly* customise a kernel for oneself will take more research than that, I reckon.

Stroller.

Re: [gentoo-user] Re: Testing new kernels - saving dumps / strip down kernel options

[Stefan G. Weichinger]

Am 10.01.2013 10:38, schrieb Nuno J. Silva:

> Even then, if you do that and tune the config several times, you'll
> likely end up with a lighter kernel. Just drop anything you don't need
> from the device drivers.
> 
>> "make allnoconfig" as a start?
> 
> That is probably much better than the config from the install dvd, yes,
> in fact most of the work coming from an "Add-It-All" config is that you
> have to disable many, many entries.

I tried with a .config from the live cd, just to see where it gets me.
Disabled loads of stuff, enabled options I need for my hardware and for
running KVM here.

This cut my .config from ~76k down to 71k already, and the kernel itself
got smaller as well:

# the backup from old .config

2,5M 10. Jan 11:52 initramfs-genkernel-x86_64-3.7.1-gentoo
3,3M 10. Jan 11:52 kernel-genkernel-x86_64-3.7.1-gentoo
2,0M 10. Jan 11:52 System.map-genkernel-x86_64-3.7.1-gentoo

# the new one

2,5M 10. Jan 13:53 initramfs-genkernel-x86_64-3.7.1-gentoo
2,7M 10. Jan 13:52 kernel-genkernel-x86_64-3.7.1-gentoo
2,1M 10. Jan 13:52 System.map-genkernel-x86_64-3.7.1-gentoo

nice so far, without much work to do.

Everything works so far, so ok ...

I might try the allnoconfig-approach as well, sure!

Stefan

Re: [gentoo-user] Testing new kernels - saving dumps / strip down kernel options

[Stefan G. Weichinger]

Am 11.01.2013 07:28, schrieb Stroller:

> I most always take the .config from a recent systemrescuecd and it
> has always worked well for me.
> 
> I change "processor type and features" and disable the initrd.

What to choose for a i7-2600 ... ?

> There may be some stuff on a LiveCD based distro which is optimised
> for running off an optical disk, so I guess a RedHat or Ubuntu
> default .config might be better.

Ah, ok, might be.
I took one from gentoo as I assumed the config might fit the
gentoo-sources better somehow (although I still don't know what patches
are applied to vanilla-sources to get gentoo-sources ... I just thought
the config might somehow make use of those changes).

> These should provide everything you need to boot, and most everything
> else as modules, which will be automatically loaded. IMO this is
> pretty much optimal.
> 
> The engineers at RedHat and Ubuntu know a heck of a lot more about
> kernels than I do. One might be able to make one's kernel
> milliseconds more efficient by tuning it by hand, but it will surely
> take hours of tinkering to attain that.
> 
> I do not believe you can properly understand the consequences of any
> given kernel option merely by reading the one- or two-line
> description in makeconfig's help. To *properly* customise a kernel
> for oneself will take more research than that, I reckon.

Yep. I don't look for those last milliseconds, I just want to get rid of
some old stuff I might drag along for years already ...

Thanks, Stefan