Parallel Decompression

[0rinsb3lt]

Noticed that on restoring a system that there was a significant amount of time checking the archive
and wondered if it could be quicker with parallel decompression. I know that pbzip2 has it.

tar supports a -I option to use other programs such as pbzip2

• tar -I pbzip2

possibly just reuse the -M --multi-core option for defining decompression (Restore mode).

[tritonas00]

possibly just reuse the -M --multi-core option for defining decompression (Restore mode).

Yes, it's possible, the code is already there for compression https://github.com/tritonas00/system-tar-and-restore/blob/master/star.sh#L529

i will look into it when i have my laptop back

[0rinsb3lt]

I did a quick patch to enable this feature for p/bzip2.

diff.txt

[tritonas00]

no need to add extra statements in read_archive

replace tf with "$BRreadopts" here https://github.com/tritonas00/system-tar-and-restore/blob/master/star.sh#L1859, and then re arrange BRreadopts here https://github.com/tritonas00/system-tar-and-restore/blob/master/star.sh#L760-L778

also i thing you need -d https://linux.die.net/man/1/pbzip2

[0rinsb3lt]

I took your suggestion with the "$BRreadopts" and here is what I came up with
diff.txt

as for the -d from what I read is that when passing a program via -I the program itself simply has to support the -d option

https://linux.die.net/man/1/tar

[tritonas00]

yes like that but the statement must be before https://github.com/tritonas00/system-tar-and-restore/blob/master/star.sh#L764 not after

when i have my laptop i will extend it to all compressors and add threads also

[0rinsb3lt]

The diff shows that After 763 in the first file (original file) it's adding the lines from the second file (one I modified). That would put them above line 764.

Other than that I think it paves the way for other compressors. ( I have another modification that adds pixz support)

[tritonas00]

The diff shows that After 763 in the first file (original file) it's adding the lines from the second file (one I modified). That would put them above line 764.

you are right, i didn't watch carefully

Other than that I think it paves the way for other compressors. ( I have another modification that adds pixz support)

exactly, but please check if non parallel way still works

fork, add your code and create a pull request

thank you for your contribution

[0rinsb3lt]

can confirm that without -M option bzip2 is used. With -M option pbzip2 is used.
#16

[tritonas00]

#16 merged, pbzip2 decompression is now done and you can use -z as well to define max threads

any idea of parallel decompressors for xz and gzip also?