[Jikesrvm-core] [ jikesrvm-Feature Requests-1208562 ] Separate code space for dynamically generated code

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Feature Requests item #1208562, was opened at 2005-05-25 11:02
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Category: GC
Group: None
Status: Open
Resolution: None
Priority: 7
Submitted By: Dave Grove (dgrove-oss)
Assigned to: Nobody/Anonymous (nobody)
Summary: Separate code space for dynamically generated code

Initial Comment:
Add a separate code space to MMTk.

Currently in Jikes RVM code and data are allocated
together (one big happy heap).  This is simple, but
opens us to a host of performance problems.  Some of
the issues are:
  (1) mixing code and mutable data causes havoc with
trace caches.
  (2) Inefficiences in allocation and GC
  (3) If the code is in a moving space, we have
problems with getting icache/dcache in sync on PPC and
general confusion of hardware predictors as the code
moves around.
  (4) Poor usage of i-TLB 
  (5) and so on, and so on.....

For bonus points, we should have two code spaces. One
for cold (baseline compiled) code and one for hot (opt
compiled) code.  This may have further slight
advantages, but the biggest win will be just having at
least one code space to segregate the code and the data.






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