Re: [gentoo-user] xz memory hungry?

[Michael Mol <mikemol@gmail.com>]

On Wed, Aug 22, 2012 at 4:43 PM, Florian Philipp <lists@binarywings.net> wrote:
> Am 22.08.2012 22:32, schrieb Jorge Almeida:
>> On Wed, Aug 22, 2012 at 8:05 PM, Michael Mol <mikemol@gmail.com> wrote:
>>> On Wed, Aug 22, 2012 at 2:52 PM, Jorge Almeida <jjalmeida@gmail.com> wrote:
>>>> # tar -xJvf /usr/portage/distfiles/m4-1.4.16.tar.xz
>>>> xz: (stdin): Cannot allocate memory
>>>>
>>>> The box has 2G ram + 1G swap. I'm installing Gentoo from an existing distro.
>>>
>>> How much do you have free? From xz's manpage:
>>
>> Almost all of it! It's a one-user workstation, which was essentialy idle.
>>>
>>>
>> I read the man page of xz, but it suggested nothing to me.
>>>
>>> Three things come to mind:
>>>
>>> 1) You may not have enough memory free
>>> 2) There may be a bug (either compile/link-induced or code-induced) in
>>> the copy of xz you're using
>>> 3) Upstream used some insane settings, causing a massive increase in
>>> the amount of RAM required to decompress that stream.
>>>
>>>
>>> You could download the .tar.xz file, decompress it on a different box,
>>> and then recompress it with lighter settings.
>>>
>>> unxz filename.tar.xz
>>> xz -1 filename.tar
>>>
>> Done that. It extracts now,  so 3) is the correct hypothesis, and  "insane" is
>> really the appropriate word. Of course, the hash digests are now wrong, so
>> emerge still fails. Any idea how to find which amount of memory is needed? I
>> would setup appropriate swap, if possible. [...]
>
> There is a table in `man xz` showing the memory requirements. Even with
> the highest setting, you only need 65 MB memory for decompression (674
> MB for compression, though).

Still not sure about this portion: "Still, it is possible to have .xz files that
require several giga‐bytes of memory to decompress."

But, yeah, this seems very wonky.

-- 
:wq