JDK-6787254 : Work queue capacity can be increased substantially on some platforms
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 5.0u15,5.0u16
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic,x86
  • Submitted: 2008-12-19
  • Updated: 2010-05-06
  • Resolved: 2009-03-25
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5.0u18-rev,hs11.3Fixed 5.0u19Fixed 6u13-revFixed 7Fixed hs11.3Fixed
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The Age field can be 64-bit in the 64-bit JVM because
of the availability of a 64-bit CAS. The resulting increase
in workqueue capacity should reduce the incidence of slow-paths
to deal with overflow handling; see for example CR 6786503.

EVALUATION Never mind; we can't have "fix failed" and then "duplicate". Will leave in state "fix delivered" but all backporters of this bug fix should know that its intentions did not take effect, and the real fix is being done in 6821693.

EVALUATION The intended change in this CR never took effect because of unintended (but thankfully benign) bugs (in this changeset) that are being fixed in 6821693. Marking this CR as fix failed and dup'ing to 6821693.

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot/hotspot/rev/23673011938d

EVALUATION http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/23673011938d


SUGGESTED FIX Preliminary shape of the changes (by no means final):- http://analemma.sfbay.sun.com/net/neeraja/export/ysr/workqueue/webrev

EVALUATION The patch for 6787254 will be sent for testing at customer once we have received test results from 6786503. The patch for 6787254 will be additive on top of those of 6786503. While the latter improves the performance in the presence of work queue overflow, the former reduces the chances of overflow with 64-bit heaps by allowing the use of larger work queues.

EVALUATION An interim patch for the fix has been generated and performance measurements are in progress. Once we are satisfied with the fix, a test binary will be generated for performance tests at the customer.