APAR status
Closed as program error.
Error description
Error Message: Fragmentation can be observed from the verbose GC log. For example: <gc-op id="2439" type="scavenge" timems="380.972" contextid="2436" timestamp="2013-05-01T16:42:49.615"> ............ <copy-failed type="tenure" objects="1567" bytes="78462824" /> <warning details="aborted collection due to insufficient free space" /> </gc-op> <gc-end id="2440" type="scavenge" contextid="2436" durationms="381.238" timestamp="2013-05-01T16:42:49.615"> <mem-info id="2441" free="287701272" total="2030829568" percent="14"> ............ <mem type="tenure" free="287701272" total="1744764928" percent="16" /> ............ </mem-info> </gc-end> There was 287MB of free memory in tenure after a scavenge. However, GC failed to tenure 78MB of objects (of average size 78462824/1567 = 50072 bytes). Clearly, the failures to tenure are not to the lack of free memory but inability to tenure lager objects of 50KB in a fragmented memory. If this occurs, next scavenge will 'precolate' to a global collection, that will likely compact the heap: <percolate-collect id="2443" from="nursery" to="global" reason="Previous scavenge failed to expand" timestamp="2013-05-01T16:42:49.615"/> ............ <gc-op id="2450" type="compact" timems="1079.814" contextid="2444" timestamp="2013-05-01T16:42:51.007"> <compact-info movecount="450116" movebytes="1078382008" reason="compact on aggressive collection" /> </gc-op> While the symptoms above are common for heap fragmentation regardless of of type/source, this specific fragmentation was introduced in Java 7 SR4. . Stack Trace: N/A .
Local fix
Problem summary
Due to object alignment large objects may require more memory than before. This may cause of these objects to have different sizes. These different sizes can lead to heap fragmentation when these objects die.
Problem conclusion
This defect will be fixed in: 7.0.0 SR5 6.0.1 SR6 . The JVM has been updated to minimize fragmentation caused by object alignment.
Temporary fix
Comments
APAR Information
APAR number
IV42295
Reported component name
J9 COMMON CODE
Reported component ID
620700127
Reported release
260
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2013-05-09
Closed date
2013-05-13
Last modified date
2013-06-14
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
J9 COMMON CODE
Fixed component ID
620700127
Applicable component levels
R260 PSY
UP
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Document Information
Modified date:
21 February 2022