From the daily build language pack LibreOfficeDev_24.8.0.0.alpha0_Linux_x86-64_deb_langpack_de.tar.gz, 7z tells that the below deb package uses the xz compression method : ------------------------------ $ 7z l libreofficedev24.8-dict-de_24.8.0.0.alpha0-1_amd64.deb [...] Type = xz Physical Size = 7713188 Method = LZMA2:23 CRC64 Streams = 1 Blocks = 4 ------------------------------ Next, I extracted the content of this deb package with the below command : 7z x libreofficedev24.8-dict-de_24.8.0.0.alpha0-1_amd64.deb This extracts the below file : data.tar Next I compressed this tar archive with xz using several compression forces : ------------------------------ $ xz -1 --threads=1 --stdout data.tar > d-1.xz $ xz -4 --threads=1 --stdout data.tar > d-4.xz $ xz -5 --threads=1 --stdout data.tar > d-5.xz $ xz -9 --threads=1 --stdout data.tar > d-9.xz ------------------------------ Looking at the size of the files, it seems the deb archive doesn't use the maximum compression force of xz : ------------------------------ $ ls -lhS * -rw-r--r-- 1 j j 82M déc. 16 03:40 data.tar -rw-r--r-- 1 j j 16M déc. 16 14:21 d-1.xz -rw-r--r-- 1 j j 11M déc. 16 14:22 d-4.xz -rw-r--r-- 1 j j 7,4M déc. 16 03:40 libreofficedev24.8-dict-de_24.8.0.0.alpha0-1_amd64.deb -rw-r--r-- 1 j j 6,7M déc. 16 14:24 d-5.xz -rw-r--r-- 1 j j 3,8M déc. 16 14:25 d-9.xz ------------------------------ The memory requirement on GNU/Linux in order to use LibreOffice is at least 256MB but prefered 512MB : https://www.libreoffice.org/get-help/system-requirements/#Linux The man page of xz tells : "decompressing a file created with xz -9 currently requires 65 MiB of memory". So there is no limitation to use the maximum force ("-9") for xz compression for a LibreOffice deb package. Users would then be able to download the deb files faster and save storage. The servers would save storage and bandwidth. As this is a single compression for many downloads, the maximum compression force for xz would provide an overall benefit.
Thanks Jérôme. Do you know what difference it makes in the time needed to decompress such packages, and overall install times? Could you test that too?
On xz decompression speed, the man page of unxz tells : "On the same hardware, the decompression speed is approximately a constant number of bytes of compressed data per second. In other words, the better the compression, the faster the decompression will usually be." My xz/unxz version : ------------- $ unxz --version xz (XZ Utils) 5.2.2 liblzma 5.2.2 $ ------------- If you want to know a part of the overall installation process performance, we can pipe the xz decompression process to file extraction process (tar in my test). I performed the below test with the core deb archive which is the largest. Of course, I ensured only one terminal ran : ------------- $ mkdir t $ dpkg-deb --extract LibreOfficeDev_24.8.0.0.alpha0_Linux_x86-64_deb/DEBS/lodevbasis24.8-core_24.8.0.0.alpha0-1_amd64.deb t $ tar cf sys-tree.tar t $ xz -9 --threads=1 --stdout sys-tree.tar > sys-tree-9.tar.xz $ xz -1 --threads=1 --stdout sys-tree.tar > sys-tree-1.tar.xz $ rm -rf t && mkdir t $ time ( unxz --to-stdout sys-tree-1.tar.xz | tar xf - --directory t ) real 0m5,969s user 0m5,992s sys 0m0,528s $ rm -rf t && mkdir t $ time ( unxz --to-stdout sys-tree-9.tar.xz | tar xf - --directory t ) real 0m5,930s user 0m5,360s sys 0m0,588s $ $ rm -rf t && mkdir t $ time ( unxz --to-stdout sys-tree-1.tar.xz | tar xf - --directory t ) real 0m6,093s user 0m6,004s sys 0m0,560s $ rm -rf t && mkdir t $ time ( unxz --to-stdout sys-tree-9.tar.xz | tar xf - --directory t ) real 0m5,905s user 0m5,368s sys 0m0,624s $ ------------- On my hardware, the core deb archive that has been compressed with the '-9' force parameter decompresses slightly faster than the archive that has been compressed with the '-1' force parameter.