JDK-6280693 : Mmap the whole jar files takes too much perceived footprint
  • Type: Bug
  • Component: core-libs
  • Sub-Component: java.util.jar
  • Affected Version: 1.4.0,5.0u17,6
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: linux,solaris,solaris_10
  • CPU: generic,x86,sparc
  • Submitted: 2005-06-06
  • Updated: 2011-06-14
  • Resolved: 2005-07-22
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Other Other Other JDK 6
5.0u29-revFixed 5.0u30-revFixed 5.0u31Fixed 6 b45Fixed
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Currently all the jar/zip files are mmaped to the address space of java application. Customers are complaining about the huge perceived footprints. One way to workaround this is to mmap part of the jar file or read it from disk.

Expriments show this could reduce percieved footprint by more than 100% on Solaris and more than 30% on Linux since rt.jar just takes too much space.
###@###.### 2005-06-06 06:48:39 GMT

EVALUATION The main reason of huge perceived footprint is because on Solaris, when you mmap a big file such as rt.jar (around 40MB), it actually shows it on "ps -ef" or "pmap -x". The solution is to read most of the jar files while still mmaping the mostly common accessed part of jar file which is central directory. Expriments show that by doing this, we could achieve both decent startup and footprint performance improvement. The webrev is at http://javaweb.sfbay.sun.com/~xl116366/webrev/fread ###@###.### 2005-07-19 03:08:57 GMT ###@###.### 2005-07-20 01:03:11 GMT