[jira] Commented: (RVM-341) Improved copying in VM_Memory

    [ http://jira.codehaus.org/browse/RVM-341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=178975#action_178975 ]

Steve Blackburn commented on RVM-341:
-------------------------------------

I have kicked off some very simple experiments by way of a limit study, comparing five systems:
  . hotspot 1.6 with aggressive runtime flags
  . our svn head
  . forcing RVMArray to _always_ use out-of-line naive java copying (no memcopy)
  . forcing RVMArray to _always_ use inline naive java copying (no memcopy)
  . forcing RVMArray to _always_ use memmove

I did this on both core 2 quad and i7.   The data is slowly dribbling in; will eventually include dacapo, jvm98 and pjbb2005.   At time of writing the following observations come to mind:
   1. all of our fancy footwork appears to buy us nothing over simply calling memmove (but wait for final results before drawing conclusions)
   2. some of the benchmarks that appear to be using array copy most (the ones that show naive as particularly punishing, such as antlr, bloat & jython at time of writing), are also ones where hotspot is punishing us heavily.
   3. for some reason memmove is killing jython.   There is no stack trace in the logs, and I've not yet investigated further.

The data:
   http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/arraycopy-i7/bmtime.jikes.html
   http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/arraycopy-c2q/bmtime.jikes.html
   http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/arraycopy-i7/bmtime.all.html
   http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/arraycopy-c2q/bmtime.all.html


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