[OE-core] [PATCH 0/3] Fix xz compression command and optimize compression time

[Andrea Adami]

On Fri, Jul 13, 2012 at 11:44 AM, Andrei Gherzan <andrei at gherzan.ro> wrote:
> On Fri, Jul 13, 2012 at 11:19 AM, Andrea Adami <andrea.adami at gmail.com>
> wrote:
>>
>> On Fri, Jul 13, 2012 at 8:45 AM, Koen Kooi <koen at dominion.thruhere.net>
>> wrote:
>> >
>> > Op 12 jul. 2012, om 21:22 heeft Saul Wold het volgende geschreven:
>> >
>> >> On 07/12/2012 11:58 AM, Koen Kooi wrote:
>> >>> Any volunteers to test this on a system with >4 real cores?
>> >>>
>> >>
>> >> Koen,
>> >>
>> >> Does OE-Core or Poky have an image setup for using .xz by default?
>> >
>> > No, and as you can see from Andrei's patches, it would have never worked
>> > :)
>> >
>> > regards,
>> >
>> > Koen
>> >
>>
>> This leads to a similar remark for lzma:
>>
>> The xz/lzma have been added with commit  38334ac and at that time both
>> where using XZ_COMPRESSION_LEVEL.
>>
>> The code has been refactored afterwards and what happened is that lzma
>> now defaults to compression 7 (the default) while xz is way too high
>> (default is 6).
>>
>
> Nope. It's default value is -9.
>

Well, in oe-core maybe.
Upstream they are more conservative, see that man.

"The default preset level in LZMA Utils is -7 while in XZ Utils it is
-6, so both use 8 MiB dictionary by default."

Cheers

Andrea

>>
>> There is a well hidden pitfall with that, being that any image,
>> including the initramfs, will use that compression factor.
>>
>> As you can notice in that (old) man xz [2]  the memory requirements
>
>
> What old version?
>
>>
>> are very high and what did happen to me was that the cpio.lzma could
>> not be decompressed thus kernel could not boot (we override now the
>> value setting "-e2" in our BSP).
>>
>
> Without threads, memory demand was around 700mb. So it should be ok for most
> of machines.
>
>> Adding more threads will multiply that figures.
>>
>
> Indeed. With 8GB memory at my disposal i couldn't compress an image with -e
> -9 and -T 0 (-T 4)/
>
> @g
>
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