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From "Scott Carey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1282) Make use of the sun.misc.Unsafe class during serialization if a JDK supports it
Date Thu, 25 Apr 2013 08:34:15 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1282?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13641569#comment-13641569
] 

Scott Carey commented on AVRO-1282:
-----------------------------------

The below appears to be a bug that assumes every class is only associated with exactly one
Schema.  If this is not the case, we could corrupt the heap or segfault by using the wrong
field accessor for the field.
{code}
  private static FieldAccessor[] getOrCreateFieldsArray(Class c, Schema schema) {
    Map<Class, FieldAccessor[]> cache = FIELDS_ARRAY_CACHE.get();  
    FieldAccessor[] fields = cache.get(c);
    if (fields == null) {
      if (schema == null)
        throw new AvroRuntimeException("No schema is known for " + c);
      fields = new FieldAccessor[schema.getFields().size()];
      cache.put(c, fields);   
      if (schema != null) {
      for (Schema.Field f: schema.getFields()) {
        getFieldAccessor(c, f.pos(), f.name());
      }
    }
  }
  return fields;
  }
{code}
                
> Make use of the sun.misc.Unsafe class during serialization if a JDK supports it
> -------------------------------------------------------------------------------
>
>                 Key: AVRO-1282
>                 URL: https://issues.apache.org/jira/browse/AVRO-1282
>             Project: Avro
>          Issue Type: Improvement
>          Components: java
>    Affects Versions: 1.7.4
>            Reporter: Leo Romanoff
>            Priority: Minor
>         Attachments: avro-1282-v1.patch, avro-1282-v2.patch, avro-1282-v3.patch, avro-1282-v4.patch,
avro-1282-v5.patch, avro-1282-v6.patch, avro-1282-v7.patch, avro-1282-v8.patch, TestUnsafeUtil.java
>
>
> Unsafe can be used to significantly speed up serialization process, if a JDK implementation
supports java.misc.Unsafe properly. Most JDKs running on PCs support it. Some platforms like
Android lack a proper support for Unsafe yet.
> There are two possibilities to use Unsafe for serialization:
> 1) Very quick access to the fields of objects. It is way faster than with the reflection-based
approach using Field.get/set
> 2) Input and Output streams can be using Unsafe to perform very quick input/output.
>  
> 3) More over, Unsafe makes it possible to serialize to/deserialize from off-heap memory
directly and very quickly, without any intermediate buffers allocated on heap. There is virtually
no overhead compared to the usual byte arrays.

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