[gentoo-amd64] Re: modules

[gentoo-amd64] Re: modules

[Duncan]

DR GM SEDDON posted <436B56B2.10106@manchester.ac.uk>, excerpted below, 
on Fri, 04 Nov 2005 12:40:18 +0000:

> Hi,
> I was wondering.  What modules do I need installed at boot?
> My hardware is
> dvd/cd rewriter  ide
> 3.5" floppy
> scsi tape drive.  initio scsi  controller
> 125 mb ati radeon graphics
> 20" sgi monitor
> 3400+ cpu
> e2800+ cellular to attatch

You don't need to load /any/ modules at boot, if you compile everything
you'd normally load at boot and never unload, into the kernel itself,
instead of as modules.

Here, I do that, but compile stuff I use only occasionally, such as the
floppy, loopback device, and parallel port (printer, yes, I still use the
parallel port for that) drivers, and the msdos (floppy), iso9660 (CD/DVD),
and ext2 (floppy) filesystems (my system is reiserfs, no ext2 unless on a
floppy or filesystem image or something), as modules, so I can load them
if an when I need them but keep the kernel from using so much unswappable
memory when I don't.

You might as well compile anything directly into the kernel that you'll be
using enough so you'd be loading the modules at boot, anyway.  The
exception would be the few items of hardware with drivers that need
parameters fed to them when loaded to get things right.  These often need
compiled and loaded as modules, even if you /do/ load them at boot and
don't ever unload them, in ordered to feed them the correct parameters
when they load.

Thus, compiled into your kernel, you'll need the IDE main and your
specific chipset drivers (or scsi drivers if you use that instead of IDE),
the file system drivers for whatever file systems you normally use, the
HID input main and keyboard drivers, virtual terminal and console on
virtual terminal, agpgart, and probably your mouse and NIC drivers, plus
motherboard or installation specific stuff like the real-time-clock, usb
drivers, etc.

Depending on how you have video setup, you likely do NOT need any kernel
graphics card drivers beyond the normal VT/console drivers for text mode. 
For use within xorg, you'll load additional xorg or proprietary drivers.

Gentoo normally recommends you compile the sound (ALSA) drivers as
modules, but I compile them in, here, figuring I use them enough I don't
want to mess with loading them separately.  Obviously, that works best if
you use the kernel's own sound drivers, rather than merging the
alsa-drivers package separately, in which case modules are easier.

As mentioned above, I don't load iso9660 or msdos filesystems or the
floppy or loopback drivers built-in or at boot, because I don't use them
enough to warrant it.  If I need them, I load them, then unload them if
I'm not immediately rebooting.  The same here for the parallel port
drivers for the printer.

Something I HAVE found I have to compile and load as modules, are the USB
stuff. However, I don't have to list them in
/etc/modules.autoload.d/kernel-2.6, because I have sys-apps/coldplug
merged and the initscript set to load as part of the boot level, and that
handles loading USB for me.  (It also handled loading the alsa/sound
modules, back when I had them compiled as modules.)

Other than that, I learned what I needed pretty much by going thru
the entire kernel config and turning on what I KNEW I needed, then
using trial and error on everything else, trying without it to see if
everything still worked and didn't complain, going back and turning it
back on if I found I needed it.  BIND, if you run it, turns out to need
something strange, that the kernel says is deprecated.  (Don't worry, tho,
enough folks run bind that deprecated or not, there WILL be a replacement
before the kernel folks can remove it for good.)  Other things you might
find you need as well.  No problem, just reboot to your old/backup if you
couldn't even boot the new kernel, turn on what you need and recompile and
reinstall the kernel, and try again.  It's tough learning it the first
time, but eventually you'll figure out what stuff you need and what most
stuff does, and be fairly familiar with kernel configuration.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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Re: [gentoo-amd64] Re: modules

[Sebastian Redl]

Duncan wrote:

>You don't need to load /any/ modules at boot, if you compile everything
>you'd normally load at boot and never unload, into the kernel itself,
>instead of as modules.
>  
>
The single exception here are binary-only modules, usually proprietary 
drivers. The ATI graphics driver fglrx comes to mind.

Sebastian Redl
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Re: [gentoo-amd64] Re: modules

[Steve Herber]

On Fri, 4 Nov 2005, Duncan wrote:

> DR GM SEDDON posted <436B56B2.10106@manchester.ac.uk>, excerpted below,
> on Fri, 04 Nov 2005 12:40:18 +0000:
>
>> Hi,
>> I was wondering.  What modules do I need installed at boot?
>
> Other than that, I learned what I needed pretty much by going thru
> the entire kernel config and turning on what I KNEW I needed, then
> using trial and error on everything else, trying without it to see if
> everything still worked and didn't complain, going back and turning it
> back on if I found I needed it....

This is why I miss RedHat.  I don't want to spend my time customizing
a kernel then spending more time with trial and error getting just the
kernel I need.  RedHat has a system in place that installs a minimal
kernal and then loads almost everything else as modules.  Genkernel almost
does what I want but it is always a struggle.  The base system always
loads all the different disk drivers and does not unload the unused ones.
Is anyone working on a more RedHat like kernel/modules/runtime loading
system?  It would eliminate the problem the original poster had and save
lots of time for the rest of us.

Thanks,

Steve Herber	herber@thing.com		work: 206-221-7262
Security Engineer, UW Medicine, IT Services	home: 425-454-2399
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Re: [gentoo-amd64] Re: modules

[Dmitri Pogosyan]

> On Fri, 4 Nov 2005, Duncan wrote: 
>  
> > DR GM SEDDON posted <436B56B2.10106@manchester.ac.uk>, excerpted below, 
> > on Fri, 04 Nov 2005 12:40:18 +0000: 
> > 
> >> Hi, 
> >> I was wondering.  What modules do I need installed at boot? 
> > 
> > Other than that, I learned what I needed pretty much by going thru 
> > the entire kernel config and turning on what I KNEW I needed, then 
> > using trial and error on everything else, trying without it to see if 
> > everything still worked and didn't complain, going back and turning it 
> > back on if I found I needed it.... 
>  
> This is why I miss RedHat.  I don't want to spend my time customizing 
> a kernel then spending more time with trial and error getting just the 
> kernel I need.  RedHat has a system in place that installs a minimal 
> kernal and then loads almost everything else as modules.  Genkernel almost 
> does what I want but it is always a struggle.  The base system always 
> loads all the different disk drivers and does not unload the unused ones. 
 
Absence of autounloading is not a property of gentoo, but of recent kernels.  
Somewhere along Linux people decided that unloading unused modules is not 
that useful :( 
 
Am I right, actually ? 
 
 
 
> Is anyone working on a more RedHat like kernel/modules/runtime loading 
> system?  It would eliminate the problem the original poster had and save 
> lots of time for the rest of us. 
>  
> Thanks, 
>  
> Steve Herber	herber@thing.com		work: 206-221-7262 
> Security Engineer, UW Medicine, IT Services	home: 425-454-2399 
> --  
> gentoo-amd64@gentoo.org mailing list 
 
 
 
-- 
Dmitri Pogosyan            Department of Physics 
Associate Professor        University of Alberta 
tel 1-780-492-2150         412 Avadh Bhatia Physics Labs 
fax 1-780-492-0714         Edmonton, AB, T6G 2J1, CANADA 
 
 
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Re: [gentoo-amd64] Re: modules

[Nuitari]

>> This is why I miss RedHat.  I don't want to spend my time customizing
>> a kernel then spending more time with trial and error getting just the
>> kernel I need.  RedHat has a system in place that installs a minimal
>> kernal and then loads almost everything else as modules.  Genkernel almost
>> does what I want but it is always a struggle.  The base system always
>> loads all the different disk drivers and does not unload the unused ones.
>
> Absence of autounloading is not a property of gentoo, but of recent kernels.
> Somewhere along Linux people decided that unloading unused modules is not
> that useful :(
>
> Am I right, actually ?

I really don't see the point of going to that much trouble to save a few 
Kbs of RAM

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Re: [gentoo-amd64] Re: modules

[Dmitri Pogosyan]

> >> This is why I miss RedHat.  I don't want to spend my time customizing
> >> a kernel then spending more time with trial and error getting just the
> >> kernel I need.  RedHat has a system in place that installs a minimal
> >> kernal and then loads almost everything else as modules.  Genkernel almost
> >> does what I want but it is always a struggle.  The base system always
> >> loads all the different disk drivers and does not unload the unused ones.
> >
> > Absence of autounloading is not a property of gentoo, but of recent kernels.
> > Somewhere along Linux people decided that unloading unused modules is not
> > that useful :(
> >
> > Am I right, actually ?
> 
> I really don't see the point of going to that much trouble to save a few 
> Kbs of RAM

General custom to be tidy is a second nature for some.

 
> -- 
> gentoo-amd64@gentoo.org mailing list



--
Dmitri Pogosyan            Department of Physics
Associate Professor        University of Alberta
tel 1-780-492-2150         412 Avadh Bhatia Physics Labs
fax 1-780-492-0714         Edmonton, AB, T6G 2J1, CANADA


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Re: [gentoo-amd64] Re: modules

[Ian Hastie]

On Fri, 4 Nov 2005 15:55:36 -0700
"Dmitri Pogosyan" <pogosyan@phys.ualberta.ca> wrote:

> Absence of autounloading is not a property of gentoo, but of recent
> kernels. Somewhere along Linux people decided that unloading unused
> modules is not that useful :( 
>  
> Am I right, actually ?

As I remember it was decided that it could be dangerous to allow
module unloading.  The main problem was that of potential for race
conditions.  For example a programme might be using a device when
another one unloaded it.  Usage counts were meant to prevent this, but
were considered unreliable.  As a result the ability to unload modules
is now a configurable option in the kernel, along with forced unloading.

-- 
Ian.

EOM
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[gentoo-amd64] Re: Re: modules

[Duncan]

Nuitari posted <Pine.LNX.4.64.0511041904550.4212@melchior.nuitari.net>,
excerpted below,  on Fri, 04 Nov 2005 19:05:39 -0500:

>> Absence of autounloading is not a property of gentoo, but of recent kernels.
>> Somewhere along Linux people decided that unloading unused modules is not
>> that useful :(
>>
>> Am I right, actually ?
> 
> I really don't see the point of going to that much trouble to save a few 
> Kbs of RAM

Ian described the kernel hackers' achieved conclusion quite accurately in
the other subthread -- module unloading wasn't seen as the route to the
most stable kernel possible, so it was deemphasized and made optional.

However, to directly comment on your reply...  yes, those few KB of RAM
/do/ matter, to many.  Consider that kernel memory is by definition
/locked/ memory -- it can never be swapped out.  On a system with uptime
into the weeks and months, not unusual at all for Linux, if you only fire
up the CD/DVD drive every couple weeks (to use a personal example that I
mentioned earlier in the thread), and that driver remains loaded all the
REST of the time as well, that's expensive space in non-swappable physical
memory that /could/ be used for (most likely) cache memory, otherwise. 
Memory is expensive, and I prefer mine doesn't sit around doing nothing,
when it can be put to better use, increasing the performance of even a
couple lookups a day that might otherwise have been flushed out of
physical memory.  It's not much, but I'd rather have it than not, since
I've paid for the memory and otherwise it's just sitting there inactive.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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