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Re: Pack200 compression of packaged jars



Le 02/05/2013 18:10, Matthias Klose a écrit :

> no, I think the question here is how an xz compressed deb without using pack200
> looks like, compared to the size of today's packages. Is this just the gain you
> would expect from switching from gzip to xz, or is this more?

Ok, I conducted another test on xerces2.jar. The baseline is the gzip
compressed jar as found in the .deb file.

  xalan2.jar           3290882 (+6.8%)
  xalan2.jar.gz        3079103
  xalan2.jar.xz        2998300 (-2.6%)

xz compression doesn't bring much in this case because the jar is
already compressed.

Here is the result with pack200:

  xalan2.jar.pack      2239001
  xalan2.jar.pack.gz    896677 (-70.8%)
  xalan2.jar.pack.xz    760432 (-75.3%)


Another test with rt.jar from the openjdk-6 package. This jar is not
compressed unlike the other jar files in /usr/share/java.

  Unpacked:
  rt.jar              52170080
  rt.jar.gz           17110391
  rt.jar.xz           10561860 (-38.3%)

  Packed:
  rt.pack             13715998
  rt.jar.pack.gz       5824549 (-65.9%)
  rt.jar.pack.xz       5065656 (-70.4%)

xz is much more efficient in this case due to the uncompressed nature of
rt.jar, but you still get a 50% improvement by throwing in pack200
compression.


> so why is having smaller debs more critical?

I don't claim this is critical, it's just a nice improvement. I wouldn't
argue for a better compression if the expected gain was only 10% or 15%.
But at 70% I think it's worth considering.


> it breaks every package which assumes that openjdk is usable during upgrades,
> partial upgrades, new installs, and so on.

I'm not sure to understand. Do you mean that a Java application could be
started at the same time openjdk is upgraded and should still function
normally? How is this possible?

Emmanuel Bourg


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