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From "Venkat Reddy (JIRA)" <axis-...@ws.apache.org>
Subject [jira] Commented: (AXIS-1771) Excessive Memory Use During Serialization/Deserialization
Date Thu, 20 Jan 2005 11:30:17 GMT
     [ http://issues.apache.org/jira/browse/AXIS-1771?page=comments#action_57830 ]
     
Venkat Reddy commented on AXIS-1771:
------------------------------------

Peter,

Here are more observations from me.

1. The tree depth reported by the MemoryTestClient is slightly incorrect. createTree(5,3)
actually constructs a tree of 6 levels with 3 children at each level.

2. Since the treesize reported is the memory footprint of the binary data, when we convert
it to SOAP message, I'm not sure how many times the size will increase. Axis is taking about
10-12 times (with multiref=false), which I think is not bad.

3. When multi-ref is true, however, we might need some fixing, because of the following -


3.1 The number of elements in the generated SOAPMessage is 4 times of that when multi-ref
is false. For example, a (2,7) tree will have 400 elements (343+49+7+1) with no multiref,
and the same will have 1600 elements with multi-ref is true. Can't say this is an issue, but
it will surely increase memory consumption.

3.2 The recursion I have reported yesterday happens only when multiref is true. The recursion
call depth is about 2*d + 3 where d is real depth of tree. So, createTree (5,3) results in
recursive calls with depth of 15 (because d is actually 6). This may be linked to the observation
3.1.

3.3 Also attached is a snapshot of recursive calls as an image (recursion.png), and SOAPMessages
generated with tree of (2,7).

So i think we may have some fixing to do only when multi-ref'ing is true. May be i'm wrong,
becuase i really don't know a thing about multi-ref'ing code, except through these test results
:)

Venkat


> Excessive Memory Use During Serialization/Deserialization
> ---------------------------------------------------------
>
>          Key: AXIS-1771
>          URL: http://issues.apache.org/jira/browse/AXIS-1771
>      Project: Axis
>         Type: Bug
>   Components: Basic Architecture
>     Versions: 1.2RC2
>  Environment: JDK 1.4.2, Mac OS X, Linux, Windows
>     Reporter: Peter Molettiere
>     Assignee: Venkat Reddy
>  Attachments: SOAPmsg_multiref_false.xml, SOAPmsg_multiref_true.xml, SerializationContext.java.diff,
memory-use-test.tgz, recursion.png
>
> Axis uses pathological amounts of memory during the serialization/deserialization process.
> We see about a 30 to 1 ratio of memory used during (de)serialization to in-memory representation
of the objects being (de)serialized. So ser/deser in axis of a 2M graph of objects uses 288M
of memory! Further, the memory used seems to scale linearly with the size of the object graph
being serialized.
> The memory used does seem to be released once serialization is done, so this isn't a
leak.
> Using the attached example code, (based on the code used to demonstrate AXIS-1423) you
can see this behavior. The test automatically runs with a max heap size of 1024M, and runs
out of memory serializing a 28M object graph. 
> As provided, it generates the following output:
> Buildfile: build.xml
> build:
>     [javac] Compiling 1 source file to /Users/pietro/Work/Axis Memory Test/build/classes
> run:
>      [java] - Unable to find required classes (javax.activation.DataHandler and javax.mail.internet.MimeMultipart).
Attachment support is disabled. 
>      [java] Created tree with 5 levels and 3 children at each level
>      [java] Axis used 13 MBytes to serialize 230 KBytes, a ratio of 30.0
>      [java] GC freed 13 MBytes
>      [java] Created tree with 5 levels and 4 children at each level
>      [java] Axis used 71 MBytes to serialize 1 MBytes, a ratio of 31.0
>      [java] GC freed 71 MBytes
>      [java] Created tree with 5 levels and 5 children at each level
>      [java] Axis used 288 MBytes to serialize 2 MBytes, a ratio of 51.0
>      [java] GC freed 287 MBytes
>      [java] Created tree with 5 levels and 6 children at each level
>      [java] Axis used 671 MBytes to serialize 11 MBytes, a ratio of 29.0
>      [java] GC freed 675 MBytes
>      [java] Created tree with 5 levels and 7 children at each level
>      [java] Out of Memory serializing 28 MBytes tree.
>      [java] Java Result: 1
> BUILD SUCCESSFUL
> Total time: 2 minutes 51 seconds
> Note that the ratios are halved from the reported values, since it includes both serialization
and deserialization of the object graph. So axis uses 30.5M to serialize a 1M message, and
another 30.5M to deserialize it, resulting in the reported 71M reported above. Also, notice
that the ratio stays close to 30 to 1 regardless of object graph size. This is the linear
scaling I mention above.
> Note also, that if you tweak the code to generate very small object graphs, you see extremely
high ratios, but I would expect this due to simple one-time overhead to operate on very small
amounts of data. That's why I start with the graph size that I do.
>  

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