FS#41721 - [systemd] build with --enable-lz4

Attached to Project: Arch Linux
Opened by test0 (test0) - Wednesday, 27 August 2014, 18:07 GMT
Last edited by Dave Reisner (falconindy) - Saturday, 13 September 2014, 15:10 GMT
Task Type Feature Request
Category Packages: Core
Status Closed
Assigned To Thomas Bächler (brain0)
Dave Reisner (falconindy)
Tom Gundersen (tomegun)
Sébastien Luttringer (seblu)
Architecture All
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 4
Private No

Details

Please add the --enable-lz4 flag; at least LZ4 is leading in speed-per-compression-ratio whereas XZ isn't.

http://compressionratings.com/sort.cgi?rating_sum.brief+4nf_pf

Drawbacks are somewhat larger journal files and an added dependency.
This task depends upon

Closed by  Dave Reisner (falconindy)
Saturday, 13 September 2014, 15:10 GMT
Reason for closing:  Won't implement
Additional comments about closing:  Until lz4 upstream demonstrates their ability to provide a sane shared library, this isn't going to happen.
Comment by Evangelos Foutras (foutrelis) - Saturday, 30 August 2014, 07:40 GMT
There are a couple of issues with LZ4 support in systemd at the moment:

1) It sometimes won't compress core dumps; I've sent a patch for this upstream. [1]

2) The generated .lz4 files are just LZ4 compressed data, missing metadata that the lz4 command-line utility requires to decompress them. [2][3] Trying to decompress a compressed core dump will result in "Error 44 :Unrecognized header : file cannot be decoded".

Problem (2) seems tricky to solve as liblz4's API doesn't provide any facilities to produce valid .lz4 files.

With the above in mind, it might be a good idea to disable lz4 for now.

[1] http://lists.freedesktop.org/archives/systemd-devel/2014-August/022775.html
[2] https://groups.google.com/forum/#!topic/lz4c/vnSY9j90_S4
[3] https://groups.google.com/forum/#!topic/lz4c/QtL9eRvYkEE
Comment by Evangelos Foutras (foutrelis) - Saturday, 30 August 2014, 08:52 GMT

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