JDK-6916968 : CMS: freeList.cpp:304 assert(_allocation_stats.prevSweep() + ..., "Conservation Principle")
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs17
  • Priority: P4
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2010-01-14
  • Updated: 2011-11-25
  • Resolved: 2011-09-30
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JDK 7 JDK 8 Other
7u2Fixed 8Fixed hs22Fixed
Related Reports
Relates :  
JDK-6631166 - CMS: better heuristics when combatting fragmentation
Relates :  
JDK-6912018 - CMS: guarantee(head() != 0,"The head of the list cannot be NULL")
Description
This assert was introduced recently in 6631166.

Failing test:-

nsk/stress/jni/gclocker/gcl001
runtime/ParallelClassLoading/mixed/combine/forName/mixed_5
Comments
EVALUATION See main CR
12-09-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/f75137faa7fe
08-07-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-comp/hotspot/rev/f75137faa7fe
08-07-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/f75137faa7fe
20-06-2011
SUGGESTED FIX Here's a preliminary set of diffs for the fix(es):- diff --git a/src/share/vm/gc_implementation/concurrentMarkSweep/freeList.cpp b/src/share/vm/gc_implementation/concurrentMarkSweep/freeList.cpp --- a/src/share/vm/gc_implementation/concurrentMarkSweep/freeList.cpp +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeList.cpp @@ -300,8 +300,21 @@ // dictionary for example, this might be the first block and // in that case there would be no place that we could record // the stats (which are kept in the block itself). - assert(_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + 1 // Total Stock + 1 - >= _allocation_stats.splitDeaths() + (ssize_t)count(), "Conservation Principle"); + assert((_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + + _allocation_stats.coalBirths() + 1) // Total Production Stock + 1 + >= (_allocation_stats.splitDeaths() + _allocation_stats.coalDeaths() + + (ssize_t)count()), // Total Current Stock + depletion + err_msg("FreeList " PTR_FORMAT " of size " SIZE_FORMAT + " violates Conservation Principle: " + "_allocation_stats.prevSweep(" SIZE_FORMAT ")" + " + _allocation_stats.splitBirths(" SIZE_FORMAT ")" + " + _allocation_stats.coalBirts(" SIZE_FORMAT ") + 1 >= " + " _allocation_stats.splitDeaths(" SIZE_FORMAT ")" + " _allocation_stats.coalDeaths(" SIZE_FORMAT ")" + " + count(" SSIZE_FORMAT ")", + this, _size, _allocation_stats.prevSweep(), _allocation_stats.splitBirths(), + _allocation_stats.splitBirths(), _allocation_stats.splitDeaths(), + _allocation_stats.coalDeaths(), count())); } void FreeList::assert_proper_lock_protection_work() const { diff --git a/src/share/vm/gc_implementation/shared/allocationStats.hpp b/src/share/vm/gc_implementation/shared/allocationStats.hpp --- a/src/share/vm/gc_implementation/shared/allocationStats.hpp +++ b/src/share/vm/gc_implementation/shared/allocationStats.hpp @@ -99,14 +99,17 @@ // vulnerable to noisy glitches. In such cases, we // ignore the current sample and use currently available // historical estimates. - // XXX NEEDS TO BE FIXED - // assert(prevSweep() + splitBirths() >= splitDeaths() + (ssize_t)count, "Conservation Principle"); - // ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - // "Total Stock" "Not used at this block size" + assert(prevSweep() + splitBirths() + coalBirths() // "Total Production Stock" + >= splitDeaths() + coalDeaths() + (ssize_t)count, // "Current stock + depletion" + "Conservation Principle"); if (inter_sweep_current > _threshold) { - ssize_t demand = prevSweep() - (ssize_t)count + splitBirths() - splitDeaths(); + ssize_t demand = prevSweep() - (ssize_t)count + splitBirths() + coalBirths() + - splitDeaths() - coalDeaths(); // XXX NEEDS TO BE FIXED - // assert(demand >= 0, "Demand should be non-negative"); + assert(demand >= 0, + err_msg("Demand (" SSIZE_FORMAT ") should be non-negative for " + PTR_FORMAT " (size=" SIZE_FORMAT ")", + demand, this, count)); // Defensive: adjust for imprecision in event counting if (demand < 0) { demand = 0;
15-06-2011
EVALUATION The "conservation principle" had been incorrectly formulated.
14-06-2011