Re: Compress images with XZ

[Matthias Fischer <matthias.fischer@ipfire.org>]

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On 29.01.2018 14:23, Michael Tremer wrote:
> Hello Matthias,

Hi Michael,

> any update on this? Are you still on this?

Sorry, no update, but its still on my list.

We had a tough time here with all kinds of diseases in the family during
the holidays and beyond, so I was only able to work on some 'easier jobs'.

Besides, I'm not really familiar with this kind of scripting, but I'll
try. This is the next I'm at.

I'll consider how I would do this and send it in as soon as I get a grip
on it.

Best,
Matthias
 > Best,
> -Michael
> 
> On Wed, 2017-11-22 at 16:37 +0000, Michael Tremer wrote:
>> Hi,
>> 
>> On Tue, 2017-11-21 at 18:35 +0100, Matthias Fischer wrote:
>> > Hi,
>> > 
>> > On 21.11.2017 15:42, Michael Tremer wrote:
>> > > Hello,
>> > > 
>> > > any progress on this?
>> > 
>> > Not much, because I've been struggling with a flu for the past two
>> > weeks, and its not over yet, but:
>> > 
>> > In the meantime I ran several builds with different parameters.
>> > 
>> > IMHO we could use:
>> > 
>> > 'export XZ_OPT = --threads=0 -8 --memory=700MiB'
>> > 
>> > in 'lfs/cdrom'
>> > 
>> > and
>> > 
>> > cd /install/packages/package/tmp/ && XZ_OPT="-T0 -8 --memory=700MiB" tar -c
>> > -p
>> > --numeric-owner -J -f /install/packages/package/files.tar.xz *
>> > 
>> > in 'lfs/Config'.
>> > 
>> > Using '9' or '--extreme'-parameter brought no further improvements,
>> > on the other hand, build time and RAM consumption increased
>> > strongly. With '-8', minimal RAM consumption was about 680 MiB, using
>> > '700 Mib' was always safe. So this is the minimum I would recommend.
>> 
>> Yes, I observed the same thing. -9 compresses a little bit better and extreme
>> doesn't change a bit.
>> 
>> -8 seems to be optimal since it won't require too much memory to decompress
>> either. So let's go with that.
>> 
>> > Results:
>> > 
>> > (Buildtime: 5 hours 20 minutes 59 seconds)
>> > 
>> > 255866764  ipfire-2.19.1gb-ext4.i586-full-core117.img.gz
>> > 252262006  ipfire-2.19.1gb-ext4-scon.i586-full-core117.img.gz
>> > 175112192  ipfire-2.19.i586-full-core117.iso
>> >  
>> > > -Michael
>> > > 
>> > > On Tue, 2017-11-07 at 22:47 +0000, Michael Tremer wrote:
>> > > > Hi,
>> > > > 
>> > > > On Tue, 2017-11-07 at 19:41 +0100, Matthias Fischer wrote:
>> > > > > Hi,
>> > > > > 
>> > > > > On 07.11.2017 16:05, Michael Tremer wrote:
>> > > > > > Hi,
>> > > > > > 
>> > > > > > maybe this function helps:
>> > > > > > 
>> > > > > > https://git.ipfire.org/?p=ipfire-2.x.git;a=commitdiff;h=5190eea24f98
>> > > > > > 22
>> > > > > > a63d
>> > > > > > c5d06d214b48f973b14f29
>> > > > > 
>> > > > > Thanks. I'll take a look...
>> > 
>> > This would help, indeed, but how to implement(!?), and... (see below)
>> 
>> Just run it somewhere in the script, figure out what is about 80% of that and
>> if
>> that is smaller than 800 MB, we should just fail.
>> 
>> It would be good to have a function that determines the xz parameters and we
>> use
>> that where ever we call xz. We don't want any duplicated code.
>> 
>> > > > > > On Tue, 2017-11-07 at 10:46 +0000, Michael Tremer wrote:
>> > > > > > > On Mon, 2017-11-06 at 22:09 +0100, Matthias Fischer wrote:
>> > > > > > > ...
>> > > > > > > > 
>> > > > > > > > I forgot: Tuning the XZ-parameters... ;-)
>> > > > > > > 
>> > > > > > > Good that you are bringing this up. So I think what we should do
>> > > > > > > here is
>> > > > > > > bringing back XZ compression with -8 so that we do not waste too
>> > > > > > > much
>> > > > > > > space
>> > > > > > > when
>> > > > > > > extracting the image again.
>> > > > > 
>> > > > > Right now I'm testing how much RAM I need.
>> > > > > 
>> > > > > Current 'next'-build is running with:
>> > > > > 
>> > > > > 'lfs/cdrom':
>> > > > > ...
>> > > > > export XZ_OPT = --threads=0 -8 --memory=500MiB
>> > > > > ...
>> > > > > 
>> > > > > 'lfs/Config':
>> > > > > ...
>> > > > > cd /install/packages/package/tmp/ && XZ_OPT="-T0 -8" ...
>> > > > > ...
>> > > > > 
>> > > > > I'm waiting for the results. Takes a while.
>> > > > 
>> > > > You can just run it like this and it will tell you:
>> > > > 
>> > > > [ms(a)hughes ~]$ xz -vv8 -T0
>> > > > xz: Filter chain: --
>> > > > lzma2=dict=32MiB,lc=3,lp=0,pb=2,mode=normal,nice=64,mf=bt4,depth=0
>> > > > xz: Using up to 4 threads.
>> > > > xz: 2,629 MiB of memory is required. The limiter is disabled.
>> > > > xz: Decompression will need 33 MiB of memory.
>> > > > xz: Compressed data cannot be written to a terminal
>> > > > xz: Try `xz --help' for more information.
>> > > > 
>> > > > > > > To not run into memory limits we should detect how much memory the
>> > > > > > > build
>> > > > > > > host
>> > > > > > > has and set the memory limit to maybe 80% of that. xz will then
>> > > > > > > automatically
>> > > > > > > scale down to a number of parallel processes that it can fit into
>> > > > > > > memory.
>> > 
>> > This is something I couldn't get to work. First, I couldn't specify not less
>> > than '700 MiB'. If I specify '600 MiB', building stops and tells me it needs
>> > at least about 680 MiB. If I use '70%', building stops. And I never saw that
>> > 'xz' "automatically scaled down". It just stopped everytime.
>> 
>> Yes, ~700M is the minimum.
>> 
>> It will just reduce the number of threads again to make sure everything fits
>> into memory.
>> 
>> >  
>> > > > > I'm a bit puzzled about this: I tried using '--memory=70%' as
>> > > > > mentioned
>> > > > > in the xz man pages, but is seems to have no effect. It looks as if
>> > > > > the
>> > > > > percent parameter isn't recognized and ignored. It always ends up in
>> > > > > "cannot allocate memory". Any hints on this? Do both 'lfs/cdrom' AND
>> > > > > 'lfs/Config' need the '--memory'-parameter?
>> > 
>> > This was the next problem: 'percent'-parameter does not work as expected.
>> 
>> No, don't use it. Just determine yourself what it is.
>> 
>> I think we could even try to set 100% of the memory, because as far as I can
>> see
>> this is worst case and xz won't use everything that we allow.
>> 
>> If that does't work, let's scale down to 90%, or 80%, etc...
>> 
>> > > > Yes, but it would be good to have one place where the parameters are
>> > > > being generated and then we just use them from a variable.
>> > 
>> > Probably beyond my capabilities for the moment. Any thoughts?
>> > 
>> > > > > > > ...
>> > > > > > > We will at least need about half a GB which should be a sensible
>> > > > > > > requirement
>> > > > > > > for a build system any ways.
>> > 
>> > I'm afraid '500 MiB' are not enough...
>> 
>> No, so we will now make 1G the minimum for a build.
>> 
>> I tried to build the OS on an ARM board with only 512MB of RAM the other day
>> and
>> even with a lot of swap it doesn't work. So we are past this any way.
>> 
>> > 
>> > > > > Agreed. Because of this I'm testing with '500Mib'.
>> > > > > 
>> > > > > > > Will you work on this bringing it into the build system?!
>> > > > > 
>> > > > > "I'll do my very best!" :-))
>> > > > 
>> > > > Very well Miss Sophie...
>> > > > ...
>> > 
>> > Best™,
>> > Matthias
>> 
>> -Michael
>