[OE-core] Results for xz compression with different -T and and -e

[Andrei Gherzan]

Hello,

Koen suggested to add -T to xz commands. We have this option implemented in
our current version .1alpha.

-T threads, --threads=threads



              Specify the number of worker threads to use.  Setting threads
to


              a special value 0 makes xz use as many threads as there are
 CPU


              cores  on  the system.  The actual number of threads can be
less


              than threads if the input file is not big enough  for
 threading


              with  the  given  settings or if using more threads would
exceed


              the memory usage limit.

-------------------

Memory: 7.8 GiB
Processor:: Intel® Core™ i5-2540M CPU @ 2.60GHz × 4

File to compress: 1.9G

xz -f -k -e -9 --check=crc32 (current configuration)
Memory: 673Mb
real    6m37.170s
user    6m35.389s
sys     0m0.884s
Compressed file size: 3.4Mb

xz -f -k -e -9 -T 4 --check=crc32
Memory: Cannot allocate memory

xz -f -k -e -8 -T 4 --check=crc32
Memory: 1.8G
real    3m24.462s
user    12m8.502s
sys     0m2.180s
Compressed file size: 3.4Mb

xz -f -k -T 4 --check=crc32 (-e defaults to -6)
Memory: 471Mb
real    1m9.265s
user    4m8.972s
sys     0m0.944s
Compressed file size: 3.4Mb

So my conclusion would be to use the default -e -6 with -T 4.

@g
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