linux-kernel - Re: [PATCH] xz: make XZ_DEC

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Date:	Sat, 8 Mar 2014 11:24:48 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Lasse Collin <lasse.collin@...aani.org>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	Phillip Lougher <phillip@...gher.demon.co.uk>,
	Kyle McMartin <kyle@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] xz: make XZ_DEC_BCJ filters non-optional

On Sat, Mar 8, 2014 at 11:11 AM, Lasse Collin <lasse.collin@...aani.org> wrote:
> On 2014-03-06 Geert Uytterhoeven wrote:
>> I once tried xz with an initrd on ARM. The kernel complained it
>> couldn't decompress the initrd, oops. I didn't investigate it at that
>> time, but probably I didn't have the x86 BCJ filter enabled, while I
>> compressed the initrd on\ amd64.
>
> With so little information I can only guess, but it sounds unlikely

I understand. Will see if I find time to retry...

> that you would have enabled the x86 BCJ filter without knowing it
> unless you used some wrapper script that does it. It's more likely that
> the ARM kernel didn't support XZ at all, you forgot --check=crc32,

I definitely didn't pass --check=crc32, just plain xz (like I'm used to plain
gzip ;-) So that's the most likely culprit.

> or it ran out of RAM due to too big LZMA2 dictionary (if you used -9,
> the decompressor allocates 64 MiB of memory, but I cannot guess how
> much RAM the target system had).

2 GiB, so that shouldn't be an issue.

> In Documentation/xz.txt under "Notes on compression options" there are
> some tips about compressing files for the in-kernel XZ decompressor.

Thanks, the --check=crc32 is indeed mentioned there.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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