Missing memory

Thu May 23 05:47:14 PDT 2013

Hi,

We have seen a few problems using the CMS collector with JBoss one of which was that the CMS collector does not collect objects that have finalizer() methods. The version of JBoss that we were using (5.1) made heavy use of objects with finalizer() methods within the implementation of its VFS component.

We ended up switching to the parallel collector which gave us maximum pause times of around 5s on a 5G heap.

- Phil
________________________________________
From: hotspot-gc-use-bounces at openjdk.java.net [hotspot-gc-use-bounces at openjdk.java.net] on behalf of Florian Binder [java at java4.info]
Sent: 23 May 2013 13:25
To: hotspot-gc-use at openjdk.java.net
Subject: Missing memory

Hi all,

I am running a jboss application with an embedded h2-database using the
CMS-Collector.
It uses the following memory configuration:
-Xms8G -Xmx8G -Xmn2G

After running a while I got the following interesting issue:
After a young collection the application uses only 3172435K (8178944K).
But In the statistics for the BinaryTreeDictionary I see only 1976982
words (~ 16MB) of Total Free Space. So I am wondering about the 2GB
which are not used and not in the free list space. Might it be in a TLAB
or PLAB or where?

The annoying problem of this occurs during the next young collection
where it does not have enough space in the old generation and fails with
"promotion failed", which results in a 17s stw collection. After this
collection I have 446204324 of Total Free Space, which seems correct.
A concurrent collection is not running due to less usage of the old
generation.

I am running it on an 8 core machine with
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode) (1.7.0_17).
Detailed information can be found below.

Thank you for your help,
Flo

############ The startup parameter are: ############
-server \
-Xms8G -Xmx8G \
-Xmn2G \
-XX:MaxPermSize=256m \
-verbose:gc \
-XX:+PrintGC \
-XX:+PrintGCDateStamps \
-XX:+PrintGCDetails \
-XX:+UseConcMarkSweepGC \
-XX:CMSInitiatingOccupancyFraction=80 \
-XX:+PrintFlagsFinal \
-XX:PrintFLSStatistics=1 \
-XX:+PrintTenuringDistribution \
-XX:+PrintGCApplicationConcurrentTime \
-XX:+PrintGCApplicationStoppedTime \
-XX:+UseLargePages \
-XX:LargePageSizeInBytes=4m \

############ The relevant gc-log snippet: ############
2013-05-23T01:04:57.536-0400: [GC Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 4459853
Max   Chunk Size: 2117113
Number of Blocks: 10
Av.  Block  Size: 445985
Tree      Height: 6
Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 6837777
Max   Chunk Size: 6832640
Number of Blocks: 6
Av.  Block  Size: 1139629
Tree      Height: 5
[ParNew
Desired survivor size 107347968 bytes, new threshold 2 (max 6)
- age   1:   59250760 bytes,   59250760 total
- age   2:   72435232 bytes,  131685992 total
: 1887488K->206257K(1887488K), 0,1177960 secs]
4788275K->3172435K(8178944K)After GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 1976982
Max   Chunk Size: 1969801
Number of Blocks: 2
Av.  Block  Size: 988491
Tree      Height: 2
After GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 6837777
Max   Chunk Size: 6832640
Number of Blocks: 6
Av.  Block  Size: 1139629
Tree      Height: 5
, 0,1179200 secs] [Times: user=0,80 sys=0,00, real=0,12 secs]
Total time for which application threads were stopped: 0,1186510 seconds
Application time: 0,7920070 seconds
2013-05-23T01:04:58.447-0400: [GC Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 1976982
Max   Chunk Size: 1969801
Number of Blocks: 2
Av.  Block  Size: 988491
Tree      Height: 2
Before GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 6837777
Max   Chunk Size: 6832640
Number of Blocks: 6
Av.  Block  Size: 1139629
Tree      Height: 5
[ParNew (promotion failed)
Desired survivor size 107347968 bytes, new threshold 2 (max 6)
- age   1:   57903280 bytes,   57903280 total
- age   2:   52076168 bytes,  109979448 total
: 1884081K->1878750K(1887488K), 2,5295040 secs][CMSCMS: Large block
0x000000071b3bb2e0
: 3020224K->2805356K(6291456K), 15,0643760 secs]
4850259K->2805356K(8178944K), [CMS Perm : 80257K->79027K(133764K)]After GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 446204324
Max   Chunk Size: 446204324
Number of Blocks: 1
Av.  Block  Size: 446204324
Tree      Height: 1
After GC:
Statistics for BinaryTreeDictionary:
------------------------------------
Total Free Space: 0
Max   Chunk Size: 0
Number of Blocks: 0
Tree      Height: 0
, 17,5940190 secs] [Times: user=18,00 sys=0,78, real=17,59 secs]
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