Re: [LinuxBIOS] [Kboot-general] Re: small 64bit initrd

[Lu, Yinghai]

Kexec support 2.4?

YH

-----Original Message-----
From: Richard Smith [mailto:[e-mail]] 
Sent: Wednesday, January 11, 2006 7:40 PM
To: Werner Almesberger
Cc: Ronald G Minnich; kboot-general(a)lists.sourceforge.net;
linuxbios(a)openbios.org; Fastboot mailing list; Lu, Yinghai
Subject: Re: [LinuxBIOS] [Kboot-general] Re: small 64bit initrd

 
 Getting 1 MB is as good as we can do for now.
 Hmm, that'll get awfully tight :-(
Its tight but can be done.  I've build a embedded system that booted
out of 1Meg of flash.  2.4 kernel+initrd that loaded a pcmcia module
for the wireless adapter in the system dhcp'ed up the network and then
pulled down a larger ramfs and kexec'ed into it.
I had to build a custom version of the pcmcia tools with uclibc only
doing the absolute minimum to get the wireless interface up.

IIRC I only had a couple of  Kb left over.

--
Richard A. Smith

[LinuxBIOS] [Kboot-general] Re: small 64bit initrd

[Richard Smith]

On 1/12/06, Lu, Yinghai <yinghai.lu(a)amd.com> wrote:
  Kexec support 2.4?
Back when Eric started it did.  2.6.x was still very new.   This was
several years ago.

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

Richard Smith <smithbone(a)gmail.com> writes:

  On 1/12/06, Lu, Yinghai <yinghai.lu(a)amd.com>
wrote:> Kexec support 2.4?>
 Back when Eric started it did.  2.6.x was still very new.  This wasseveral years
 ago.
2.4 is still fairly easy to get going.  The problem is all of the related
hardware fixes which are hard to identify and back port.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Steve Gehlbach]

If you could provide a roadmap on how to do this, or even better have a 
chance to do it yourself for 2.4.27+ (2.4.32 would be great), that would 
_really_ be useful.

2.4 is a smaller kernel than 2.6, and for supporting legacy systems that 
only boot from floppies, I regularly use it on a single boot floppy, 
using uclibc and busybox, along with e2fs tools and also dialog, for 
lots of support software we develop.  I guess we have a thing about 
getting it all on one floppy, but it would be helpful if we could jump 
into a 2.6 kernel on CD, for some situations.  Legacy systems won't boot 
from CD in most cases.

Steve G.




Eric W. Biederman wrote:

 Richard Smith <smithbone(a)gmail.com> writes:

  

 On 1/12/06, Lu, Yinghai <yinghai.lu(a)amd.com>
wrote:> Kexec support 2.4?>
Back when Eric started it did.  2.6.x was still very new.  This wasseveral years
ago.
    
2.4 is still fairly easy to get going.  The problem is all of the related
hardware fixes which are hard to identify and back port.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Richard Smith]

On 1/13/06, Steve Gehlbach <steve(a)nexpath.com> wrote:

  If you could provide a roadmap on how to do this, or
even better have a
 chance to do it yourself for 2.4.27+ (2.4.32 would be great), that would
 _really_ be useful.

 2.4 is a smaller kernel than 2.6, and for supporting legacy systems that
 only boot from floppies, I regularly use it on a single boot floppy,
 using uclibc and busybox, along with e2fs tools and also dialog, for
Is is smaller than a linux tiny kernel?

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Steve Gehlbach]

Not sure, I am not familiar with that.  But 2.4.32 comes in at around 
948K with ext2/3, isofs, dosfs, usb/ms, and about a dozen network card 
drivers.  Busybox with most programs enabled along with dialog, mke2fs 
and e2fsck spliced in as addons, is about 720K (uncompressed), and the 
whole thing with a few of our shell scripts is about 40K under the 1.44M 
limit.

Steve G.


Richard Smith wrote:

 On 1/13/06, Steve Gehlbach <steve(a)nexpath.com>
wrote:

  

 If you could provide a roadmap on how to do this,
or even better have a
chance to do it yourself for 2.4.27+ (2.4.32 would be great), that would
_really_ be useful.

2.4 is a smaller kernel than 2.6, and for supporting legacy systems that
only boot from floppies, I regularly use it on a single boot floppy,
using uclibc and busybox, along with e2fs tools and also dialog, for
    
Is is smaller than a linux tiny kernel?

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Richard Smith]

On 1/13/06, Steve Gehlbach <steve(a)nexpath.com> wrote:

  Not sure, I am not familiar with that.  But 2.4.32
comes in at around
 948K with ext2/3, isofs, dosfs, usb/ms, and about a dozen network card
Linux-tiny may be able to  beat that.  The number in the orginal paper
was a TCP/IP, ext2, PCI and 1 network card in 363k.

Give it a whirl and report back your results.

http://www.selenic.com/linux-tiny/

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Steve Gehlbach]

Well, linux-tiny does do better, but so far it seems to have too many 
bugs in 2.6.14 for serious work.  Many config setting I tried give 
compile errors, which seem to be related to unenforced dependencies, and 
even when I can get it to compile I have never had it actually work, 
erroring out in the boot process with "bad gzip magic number".  But I 
have gotten unpatched 2.6.14 to work, with kexec, and successfully 
jumped into knoppix from a single floppy boot with all the tools I 
need.  Thanks for the help, right now the -Os compile switch gets me 
there, and I will keep monitoring linux-tiny for additional progress.

Steve G.


Richard Smith wrote:

 On 1/13/06, Steve Gehlbach <steve(a)nexpath.com>
wrote:

  

 Not sure, I am not familiar with that.  But 2.4.32
comes in at around
948K with ext2/3, isofs, dosfs, usb/ms, and about a dozen network card
    
Linux-tiny may be able to  beat that.  The number in the orginal paper
was a TCP/IP, ext2, PCI and 1 network card in 363k.

Give it a whirl and report back your results.

http://www.selenic.com/linux-tiny/

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

Steve Gehlbach <steve(a)nexpath.com> writes:

  If you could provide a roadmap on how to do this, or
even better have a chance
 to do it yourself for 2.4.27+ (2.4.32 would be great), that would _really_ be
 useful.

 2.4 is a smaller kernel than 2.6, and for supporting legacy systems that only
 boot from floppies, I regularly use it on a single boot floppy, using uclibc and
 busybox, along with e2fs tools and also dialog, for lots of support software we
 develop.  I guess we have a thing about getting it all on one floppy, but it
 would be helpful if we could jump into a 2.6 kernel on CD, for some situations.
 Legacy systems won't boot from CD in most cases.
I did some measurements in early 2.6.  Using the patches from the linux tiny
tree.  2.6 was comparable with 2.2 and noticeably smaller than  2.4.

Basically my conclusion is that 2.6 was only bigger because it had more
stuff in it by default and almost all of that stuff is configurable.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[yhlu]

Eric,

are you sure the linux tiny will be in 2.6.16?

YH

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Steve Gehlbach]

Thanks for the info.  I will give it a try.  I actually had linux-tiny 
in my list of links to get to and read, and hadn't got there yet.  A few 
months ago I just took a straight forward approach of clicking the same 
things I had in 2.4 for 2.6, and it built out at about 1300K.  It was so 
far from 900K that I didn't look any further.  Things that I need that 
add a lot are for example usb mass storage and also ext3 but I am not 
sure how much that adds.

I might also mention that I have always left out module support, and 
linked in 5-10 most popular network drivers.  There seems to be no 
savings in space since you would need all the modules on the disk 
anyway.  Never had any problems in the drivers finding their card or 
conflicting.  The idea is that it can be used on a wide variety of 
hardware without configuration.  Maybe others have a better approach I 
am open for ideas.

Steve G.


Eric W. Biederman wrote:

 I did some measurements in early 2.6.  Using the
patches from the linux tiny
tree.  2.6 was comparable with 2.2 and noticeably smaller than  2.4.

Basically my conclusion is that 2.6 was only bigger because it had more
stuff in it by default and almost all of that stuff is configurable.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

Steve Gehlbach <steve(a)nexpath.com> writes:

  Thanks for the info.  I will give it a try.  I
actually had linux-tiny in my
 list of links to get to and read, and hadn't got there yet.  A few months ago I
 just took a straight forward approach of clicking the same things I had in 2.4
 for 2.6, and it built out at about 1300K.  It was so far from 900K that I didn't
 look any further.  Things that I need that add a lot are for example usb mass
 storage and also ext3 but I am not sure how much that adds.

 I might also mention that I have always left out module support, and linked in
 5-10 most popular network drivers.  There seems to be no savings in space since
 you would need all the modules on the disk anyway.  Never had any problems in
 the drivers finding their card or conflicting.  The idea is that it can be used
 on a wide variety of hardware without configuration.  Maybe others have a better
 approach I am open for ideas.
The two interesting pieces for your style of configuration are:
1) The -Os work that has been going on recently, I think I have
   heard 10% reduction for that.
2) Careful selection of which compiler you are using as that makes
   a noticeable difference.
3) Look under CONFIG_EMBEDDED and possibly elsewhere for options
   you don't need and can turn off.  CONFIG_EMBEDDED also has some
   smaller alternatives for some of the common features.

You might also grab ext2 instead of ext3.  When clean either will
work.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[steve]

Thanks hugely for the suggestions.  I need ext3 since this build is also 
used for rebuilding or fixing filesystems but you make a good point.

One of the errors that I made previously, and I appreciate everyone 
pointing out that 2.6 was not necessarily larger than 2.4, is that I did 
not carefully go down each tree in the menuconfig.  At the time I did 
not realize that 2.6 had so many options and buried menus.

I put in the linux-tiny patch for 2.6.14, and after working on the 
config for an hour or so, I got it down to 1020K with gcc-3.3.  Based on 
Eric's suggestions, I took the same config and put it on a system with 
gcc-4.0, put in the -Os option, and got a size of 814K!  This is with 
all I need in the kernel and the kexec option.  If you recall my limit 
is about 950K-960K so this is perfect.  I am assuming the kexec tools 
needs clib so I will have to splice this into busybox somehow but 
hopefully it won't add too much.

I haven't made sure it all works yet, but it is close enough to start 
debugging.  Thanks tremendously for all the help.

Steve G.

Eric W. Biederman wrote:

 
The two interesting pieces for your style of configuration are:
1) The -Os work that has been going on recently, I think I have
   heard 10% reduction for that.
2) Careful selection of which compiler you are using as that makes
   a noticeable difference.
3) Look under CONFIG_EMBEDDED and possibly elsewhere for options
   you don't need and can turn off.  CONFIG_EMBEDDED also has some
   smaller alternatives for some of the common features.

You might also grab ext2 instead of ext3.  When clean either will
work.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[Richard Smith]

  gcc-4.0, put in the -Os option, and got a size of
814K!  This is with
 all I need in the kernel and the kexec option.  If you recall my limit
 is about 950K-960K so this is perfect.  I am assuming the kexec tools
 needs clib so I will have to splice this into busybox somehow but
 hopefully it won't add too much.
If you want to try and go further then:

http://redhat.com/~mingo/debloating-patches/

They are for 2.6.16 though so you will need to go into developent
territory.  Ingo claims a extra  5% or 6% size reduction.  Its not
clear if this is with or irrespective of the tiny patches.

--
Richard A. Smith

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

steve <steve(a)nexpath.com> writes:

  I put in the linux-tiny patch for 2.6.14, and after
working on the config for an
 hour or so, I got it down to 1020K with gcc-3.3.  Based on Eric's suggestions, I
 took the same config and put it on a system with gcc-4.0, put in the -Os option,
 and got a size of 814K!  This is with all I need in the kernel and the kexec
 option.  If you recall my limit is about 950K-960K so this is perfect.  I am
 assuming the kexec tools needs clib so I will have to splice this into busybox
 somehow but hopefully it won't add too much.
It looks like Werner already has it working against uclibc.
/sbin/kexec is not especially demanding of libc.

Eric

[LinuxBIOS] [Fastboot] Re: [Kboot-general] Re: small 64bit initrd

[steve]

kexec compiles fine under uclibc tool chain with about 196K dynamic 
exec. That compresses to 61K so I think it will fit.

Steve G.

Eric W. Biederman wrote:

 steve <steve(a)nexpath.com> writes:

  

 I put in the linux-tiny patch for 2.6.14, and
after working on the config for an
hour or so, I got it down to 1020K with gcc-3.3.  Based on Eric's suggestions, I
took the same config and put it on a system with gcc-4.0, put in the -Os option,
and got a size of 814K!  This is with all I need in the kernel and the kexec
option.  If you recall my limit is about 950K-960K so this is perfect.  I am
assuming the kexec tools needs clib so I will have to splice this into busybox
somehow but hopefully it won't add too much.
    
It looks like Werner already has it working against uclibc.
/sbin/kexec is not especially demanding of libc.

Eric