JDK-7039627 : G1: avoid BOT updates for survivor allocations and dirty survivor regions incrementally
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs21
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2011-04-26
  • Updated: 2013-09-18
  • Resolved: 2011-09-30
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7u2Fixed 8Fixed hs22Fixed
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Description
Currently when we allocate objects into survivor regions during GC we actually update the BOT even though we don't need to (we'll never have to scan cards on survivor regions so we won't need to do BOT look-ups for those regions). Additionally, we dirty the cards on the survivor regions as an extra pass at the end of the GC.

We should improve the above by:

a) Avoid BOT updates for survivor regions (like we do for mutator allocations), and
b) Dirty the cards on survivor regions incrementally, upon every allocation (like, again, we do for mutator allocations)

We now have a G1AllocRegion abstraction in G1 (pushed as part of 7023151) that we use for mutator allocation regions. We should re-use it for GC allocation regions too given that we currently have a lot of code replication.

Comments
EVALUATION See main CR
12-09-2011

EVALUATION http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/f44782f04dd4
17-08-2011

EVALUATION http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/rev/f44782f04dd4
17-08-2011

EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/f44782f04dd4
12-08-2011

EVALUATION See Description.
26-04-2011