cvs commit: src/sys/boot/i386/libi386 biosmem.c i386_copy.c libi386.h src/sys/boot/i386/loader main.c

[Brian Fundakowski Feldman]

On Wed, Dec 21, 2005 at 09:30:39AM -0800, Maxim Sobolev wrote:
> Brian Fundakowski Feldman wrote:
> >On Wed, Dec 21, 2005 at 02:17:59AM +0000, Maxim Sobolev wrote:
> >>sobomax     2005-12-21 02:17:58 UTC
> >>
> >>  FreeBSD src repository
> >>
> >>  Modified files:
> >>    sys/boot/i386/libi386 biosmem.c i386_copy.c libi386.h 
> >>    sys/boot/i386/loader main.c 
> >>  Log:
> >>  For the cases when loading bzip2-compressed kernels enabled use last
> >>  3MB of physical memory for heap instead of range between 1MB and 4MB.
> >>  This makes this feature working with PAE and amd64 kernels, which are
> >>  loaded at 2MB. Teach i386_copyin() to avoid using range allocated by
> >>  heap in such case, so that it won't trash heap in the low memory
> >>  conditions.
> >>  
> >>  This should make loading bzip2-compressed kernels/modules/mfs images
> >>  generally useable, so that re@ team is welcome to evaluate merits
> >>  of using this feature in the installation CDs.
> >>  
> >>  Valuable suggestions by:        jhb
> >
> >Should probably just be using 7-zip instead, though.
> 
> Huh? Are you going to add appropriate loader(8) support? Besides, 7-zip 
> apparently even more memory hungry than bzip2:
> 
>   d{N}:   Sets Dictionary size - [0, 28], default: 23 (8MB)
>           The maximum value for dictionary size is 256 MB = 2^28 bytes.
>           Dictionary size is calculated as DictionarySize = 2^N bytes.
>           For decompressing file compressed by LZMA method with dictionary
>           size D = 2^N you need about D bytes of memory (RAM).
> 
> sobomax at bugor$ lzma e /tmp/kernel /tmp/kernel.lzma
> 
> LZMA 4.17 Copyright (c) 1999-2004 Igor Pavlov  2005-04-18
> sobomax at bugor$ ls -l /tmp/kernel.lzma
> -rw-r--r--  1 sobomax  wheel  1289963 21 ?????? 08:05 /tmp/kernel.lzma
> sobomax at bugor$ bzip2 -9 /tmp/kernel
> sobomax at bugor$ ls -l /tmp/kernel.bz2
> -r-xr-xr-x  1 sobomax  wheel  1514551 21 ?????? 08:04 /tmp/kernel.bz2
> sobomax at bugor$ sudo bunzip2 /tmp/kernel.bz2
> sobomax at bugor$ lzma e /tmp/kernel /tmp/kernel.lzma -d11
> 
> LZMA 4.17 Copyright (c) 1999-2004 Igor Pavlov  2005-04-18
> sobomax at bugor$ ls -l /tmp/kernel.lzma
> -rw-r--r--  1 sobomax  wheel  1550520 21 ?????? 08:10 /tmp/kernel.lzma
> 
> As you can see, when memory size available for decompression is a 
> concern (roughly 2MB in this example) bzip2 provides comparable compression.

5.2 Single-call Decompressing with input stream callback
--------------------------------------------------------
When to use: File->RAM or Flash->RAM decompressing.
Compile files: LzmaDecode.h, LzmaDecode.c
Compile defines: _LZMA_IN_CB
Memory Requirements:
  - Buffer for input stream: any size (for example, 16 KB)
  - Output buffer: uncompressed size
  - LZMA Internal Structures (~16 KB for default settings)

So adding up the dictionary sizes and limiting it to 2MB, using
compression that optimizes x86 executable storage, LZMA instead of
bzip2, solid archiving, we get:

{"/home/green" green at green}$ du -sk kernel.*
5328    kernel.7z
8070    kernel.bzip2-4ed
8038    kernel.bzip2-8ed
19406   kernel.straight

I would see those as considerable savings.

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green at FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\