[OE-core] [PATCH 0/3] Fix xz compression command and optimize compression time

[Andrei Gherzan]

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 0.

The following changes since commit 90ad663909c0c8a405b22a510c9f957007d02669:

  upstream_tracking: update boost (2012-07-09 17:21:38 +0100)

are available in the git repository at:

  git://git.yoctoproject.org/poky-contrib ag/xz
  http://git.yoctoproject.org/cgit.cgi/poky-contrib/log/?h=ag/xz

Andrei Gherzan (3):
  image_types.bbclass: Fix COMPRESS_CMD for xz to redirect compressed
    data to file
  image_types.bbclass: Add XZ variable to set number of threads to be
    used while compressing
  image_types.bbclass: Default XZ_COMPRESSION_LEVEL to -e -6

 meta/classes/image_types.bbclass |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

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