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Old 07-01-2012, 03:03 PM
Milan Kupcevic
 
Default Bug#549681: mkvmlinuz: use xz to compress vmlinuz-boxed initrd

On 07/01/2012 07:05 AM, Touko Korpela wrote:
>> ...
>> +if test "$post_2_6_38"; then
>> + XZ="xz --check=crc32 -8"
>> +else
>> + XZ=false
>> +fi
>
> From xz(1) manual page (you can ignore DecMem):
> Preset DictSize CompCPU CompMem DecMem
> -0 256 KiB 0 3 MiB 1 MiB
> -1 1 MiB 1 9 MiB 2 MiB
> -2 2 MiB 2 17 MiB 3 MiB
> -3 4 MiB 3 32 MiB 5 MiB
> -4 4 MiB 4 48 MiB 5 MiB
> -5 8 MiB 5 94 MiB 9 MiB
> -6 8 MiB 6 94 MiB 9 MiB
> -7 16 MiB 6 186 MiB 17 MiB
> -8 32 MiB 6 370 MiB 33 MiB
> -9 64 MiB 6 674 MiB 65 MiB
>
> Better to use default setting "-6" that has lower memory requirement.
>

Here is timing for re-compression from gzip to xz on Pegasos II with
Freescale 7447 1GhZ processor and 1Gb RAM:

set time compressed size
-9 1m43.962s 9.5MB
-8 1m44.824s 9.5MB
-6 1m35.097s 9.6MB
-3 1m10.080s 10.6MB
-2 0m45.609s 10.7MB
-0 0m19.286s 11.1MB

I've originally decided to go with -8, mainly because the same preset is
used in mkinitramfs form initramfs-tools package. It may be worth
hearing arguments about the timing given that all presets currently
produce vmlinuz smaller than the 12MB limit, but the compression time is
very different.

Milan
 
Old 07-02-2012, 11:07 AM
Touko Korpela
 
Default Bug#549681: mkvmlinuz: use xz to compress vmlinuz-boxed initrd

On Sun, Jul 01, 2012 at 11:03:02AM -0400, Milan Kupcevic wrote:
> On 07/01/2012 07:05 AM, Touko Korpela wrote:
> >> ...
> >> +if test "$post_2_6_38"; then
> >> + XZ="xz --check=crc32 -8"
> >> +else
> >> + XZ=false
> >> +fi
> >
> > From xz(1) manual page (you can ignore DecMem):
> > Preset DictSize CompCPU CompMem DecMem
> > -0 256 KiB 0 3 MiB 1 MiB
> > -1 1 MiB 1 9 MiB 2 MiB
> > -2 2 MiB 2 17 MiB 3 MiB
> > -3 4 MiB 3 32 MiB 5 MiB
> > -4 4 MiB 4 48 MiB 5 MiB
> > -5 8 MiB 5 94 MiB 9 MiB
> > -6 8 MiB 6 94 MiB 9 MiB
> > -7 16 MiB 6 186 MiB 17 MiB
> > -8 32 MiB 6 370 MiB 33 MiB
> > -9 64 MiB 6 674 MiB 65 MiB
> >
> > Better to use default setting "-6" that has lower memory requirement.
> >
>
> Here is timing for re-compression from gzip to xz on Pegasos II with
> Freescale 7447 1GhZ processor and 1Gb RAM:

Use of -8 option isn't a good thing for systems having only 512 Mib or less
memory. This operation shouldn't force to use slow swap space or OOM.

>
> set time compressed size
> -9 1m43.962s 9.5MB
> -8 1m44.824s 9.5MB
> -6 1m35.097s 9.6MB
> -3 1m10.080s 10.6MB
> -2 0m45.609s 10.7MB
> -0 0m19.286s 11.1MB
>
> I've originally decided to go with -8, mainly because the same preset is
> used in mkinitramfs form initramfs-tools package. It may be worth
> hearing arguments about the timing given that all presets currently
> produce vmlinuz smaller than the 12MB limit, but the compression time is
> very different.

Your size numbers show that -8 produces only marginally smaller images.
If mkinitramfs (initramfs-tools) uses -8 for xz compression, it should be
changed too.



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Old 07-03-2012, 01:13 AM
Milan Kupcevic
 
Default Bug#549681: mkvmlinuz: use xz to compress vmlinuz-boxed initrd

On 07/02/2012 07:07 AM, Touko Korpela wrote:
> On Sun, Jul 01, 2012 at 11:03:02AM -0400, Milan Kupcevic wrote:
>> On 07/01/2012 07:05 AM, Touko Korpela wrote:
>>>> ...
>>>> +if test "$post_2_6_38"; then
>>>> + XZ="xz --check=crc32 -8"
>>>> +else
>>>> + XZ=false
>>>> +fi
>>>
>>> From xz(1) manual page (you can ignore DecMem):
>>> Preset DictSize CompCPU CompMem DecMem
>>> -0 256 KiB 0 3 MiB 1 MiB
>>> -1 1 MiB 1 9 MiB 2 MiB
>>> -2 2 MiB 2 17 MiB 3 MiB
>>> -3 4 MiB 3 32 MiB 5 MiB
>>> -4 4 MiB 4 48 MiB 5 MiB
>>> -5 8 MiB 5 94 MiB 9 MiB
>>> -6 8 MiB 6 94 MiB 9 MiB
>>> -7 16 MiB 6 186 MiB 17 MiB
>>> -8 32 MiB 6 370 MiB 33 MiB
>>> -9 64 MiB 6 674 MiB 65 MiB
>>>
>>> Better to use default setting "-6" that has lower memory requirement.
>>>
>>
>> Here is timing for re-compression from gzip to xz on Pegasos II with
>> Freescale 7447 1GhZ processor and 1Gb RAM:
>
> Use of -8 option isn't a good thing for systems having only 512 Mib or less
> memory. This operation shouldn't force to use slow swap space or OOM.
>
>>
>> set time compressed size
>> -9 1m43.962s 9.5MB
>> -8 1m44.824s 9.5MB
>> -6 1m35.097s 9.6MB
>> -3 1m10.080s 10.6MB
>> -2 0m45.609s 10.7MB
>> -0 0m19.286s 11.1MB
>>
>> I've originally decided to go with -8, mainly because the same preset is
>> used in mkinitramfs form initramfs-tools package. It may be worth
>> hearing arguments about the timing given that all presets currently
>> produce vmlinuz smaller than the 12MB limit, but the compression time is
>> very different.
>
> Your size numbers show that -8 produces only marginally smaller images.
> If mkinitramfs (initramfs-tools) uses -8 for xz compression, it should be
> changed too.
>

You are right. I just did two more runs with -4 and -5:

set time compressed size
-5 1m28.009s 9.6MB
-4 1m12.628s 9.8MB

Compression time goes up while compression gain gets insignificant with
presets larger than -4.

It is probably best to go with -4. It is time efficient and needs only
48 MiB for compression. Installer will be able to finish on EFIKA 5200B
boards with 128MB built-in memory.

Milan
 

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