untar with plzip faster than with lzip for no apparent reason

[wrotycz]

I found this, interesting thing - when untarring single member lzip compressed tar plzip turnes out to be apparently faster than lzip,

despite the fact that that archive is single member and pure decompression is faster with lzip.

It also has something to do with nuber of files in tar archive - when tested with very few files like silesia.tar,

effect did not appear.

It is not, in any way, life changing situation but interesting anomaly.

I wonder what could be a reason for that.

~~~

$ lzip -lv binutils-2.43.tar.lz

   dict   memb  trail   uncompressed     compressed   saved  name

  32 MiB     1      0      326164480       27688115  91.51%  binutils-2.43.tar.lz

//// test

$ time lzip -t silesia.tar.lz

real    0m7.340s

user    0m7.260s

sys     0m0.063s

$ time plzip -n4 -t silesia.tar.lz

real    0m8.189s

user    0m8.105s

sys     0m0.075s

//// untar

$ time lzip -dc binutils-2.43.tar.lz | tar -xf-

real    0m7.552s

user    0m5.728s

sys     0m2.363s

$ time plzip -n1 -dc binutils-2.43.tar.lz | tar -xf-

real    0m6.415s

user    0m6.331s

sys     0m3.313s

$ time plzip -n4 -dc binutils-2.43.tar.lz | tar -xf-

real    0m6.424s

user    0m6.290s

sys     0m3.370s

~~~

More details in attachment.

untar-tlz-n.txt
Description: Text document