How to unpack bzip2 faster using parallel approach?

There are multiple tools which claim option to decompress bzip2 in parallel:

• pbzip2
• lbzip2

Let's compare pbzip2 performance with reference singe thread bzip2:

$ time bzip2 -d /tmp/rib.bz2  --stdout > /dev/null

real 0m52.188s

user 0m52.019s

sys 0m0.160s

$ time pbzip2 -d /tmp/rib.bz2  --stdout > /dev/null

real 0m49.380s

user 0m49.473s

sys 0m0.241s

You may notice that we have no speed improvement at all which means that pbzip2 cannot do decompression in parallel for standard bz2 compressed files.

But lbzip2 actually can do it and it offers great performance improvement:

$ time bzip2 -d /tmp/rib.bz2  --stdout > /dev/null

real 0m52.790s

user 0m52.549s

sys 0m0.224s

$ time lbzip2 -d /tmp/rib.bz2   --stdout > /dev/null

real 0m8.604s

user 1m8.099s

sys 0m0.420s

It's 9 seconds vs 53 seconds. It's 6 times improvement on 8 CPU server. 

Conclusions: use lbzip2 for parallel decompression.