Fast Infoset performance reports

Fast Infoset performance reports have been generated from executing Japex configuration files (for the efficiency of parsing, serializing and size) for the following infosets:

  • General XML infosets

  • UBL XML infosets; and

  • FpML XML infosets.

The FastInfosetPerformance sub-project contains directories corresponding to General, UBL and FpML. Each contains a set of data to be measured (XML documents) and Japex configuration files for executing performance tests to produce results for parsing, serializing and size efficiency of the data. The Japex drivers that are used to measure the parsing, serializing and size efficiency are available in the JapexXMLDriverLibrary sub-project. Thus everything is available to independently verify any results presented. It is highly recommend to verify such results and to modify the Japex configuration to test with data specific to appropriate use-cases and also to test other parsers. (If there are any issues with verification results or modification of Japex configuration files please email the users email list with questions.)

As of writing (6. October 2005) the Japex configuration files were used to produce reports linked in the following table.


General

UBL

FpML

Parse

Japex report

Japex report

Japex report

Serialize

Japex report

Japex report

Japex report

Size

Japex report

Japex report

Japex report



Measurements

All measurements were performed on an Acer 3400 running Solaris 11 using Sun's 1.5.0_04-b05 JDK. The following Java options were used: -server -XX:+UseJumpTables -Xms384m -Xmx384m.

The General parse measurements compare the Fast Infoset SAX and StAX parsers (in various configurations, see later for an explanation) with the Xerces 2.7.1 SAX parser and the Sun SJSXP StAX parser. The UBL and FpML parsing measurements compare the Fast Infoset SAX parser (in various configurations) with the Xerces 2.7.1 SAX parser.

The serialize measurements compare the Fast Infoset DOM serializer (in various configurations) with the Xerces 2.7.1 DOM XMLSerializer.

The size measurements compare the size of fast infoset documents (produced from various serialization configurations) with the original XML documents, and the size of GZIP'ing (using default compression settings) both types of document.

The various configurations mentioned previously refer to application of Fast Infoset features. The Fast Infoset encoding has a number of features that can affect the efficiency and parsing, serializing and size. Two such features are used:

  1. Indexing of content (see “The Basic Concept of Indexing” section of this paper). A Fast Infoset serializer can index repeating text content or repeating attribute values. For example, if an attribute value of “true” appears more than once in an XML document then for a fast infoset document if “true” is indexed it will occur literally for the first occurrence then for the second and subsequent occurrences a (usually small) integer value is encoded instead of the string. The latter takes less space then the former and may result in smaller fast infoset documents (potentially at the expense of serialization and parsing efficiency, although this could be offset against of the costs of encoding and decoding literal strings encoded in say UTF-8 or UTF-16). The Fast Infoset serializers support a simple heuristic that any content less than 'n' characters will be indexed, the default value of 'n' being 7 characters (for both text content and attribute values).

  2. External vocabulary (see “Types of Vocabularies” section of this paper). A Fast Infoset serializer can avoid the encoding of strings for tags, prefixes and namespace names and instead encode (usually small) integer values. This requires that the Fast Infoset serializer and parser agree (out-of-band) what the integer values are for strings. The use of encoding algorithms can reduce the size of fast infoset documents for small documents as well as increase the efficiency of parsing and serialization.

A Japex driver that contains the string 'IndexedContent' in its name with a number, 'x' say, before the string means that content less than 'x' characters will be indexed when creating fast infoset documents (for example the driver 'FastInfoset24IndexedContentSAXDriver', is the driver testing the Fast Infoset SAX parser for the parsing of Fast Infoset documents created using a Fast Infoset serializer that indexes content less than 24 characters).

A Japex driver that contains the string 'ExtVocab' in its name means that an external vocabulary has been used to create the fast infoset document from an XML infoset. In this case the external vocabulary of a XML infoset is calculated from the XML infoset itself. This is not the normal practice for the generation of such a vocabulary. For testing purposes it represents the most optimal form of encoding. In reality an external vocabulary would be generated from other information like W3C XML Schema and/or a large set of instances where the common repeating strings are assigned the smallest indexes. In this respect it is expected that the optimized non-practical external vocabulary will not deviate too much from one used in practice.

Observations on parse results

On average the Fast Infoset SAX parser (using default settings) is about 5 times faster than the Xerces 2.7.1 SAX parser and about 4 times faster than the Sun The Sun SJSXP StAX parser is one of the fastest and conforming Java-based parsers there is and is 5 to 20% faster than Xerces 2.7.1.

The Fast Infoset StAX parser is slower than the Fast Infoset SAX. It is not precisely clear why this is the case as the two implementations share a common code base. One possibility is that hotspot engine is generating run-time code for the the shared Java code for the use-case of the SAX parser (since the SAX-based tests are run first) and the run-time code is not as optimal when used with the StAX parser. Another possibility is that the hotspot can optimize more efficiently the push-based approach of SAX parsing better than the pull-based approach of StAX parsing because the former controls the pushing of events in a 'tight-loop'. More investigation is required to understand why such differences occur.

Indexing of content for less than 16 or 24 characters (instead of the default 7) can result in better parsing performance (between 2 to 10%, relative to XML) for infosets that contain such redundant information.

For 'small' XML infosets (the UBL and FpML infosets, which also contain a lot of different tags) an external vocabulary can approximately double the speed of the Fast Infoset SAX parser in some individual tests. On average the Fast Infoset SAX parser is about 7 times to 8 times faster than the Xerces 2.7.1 SAX parser for UBL and FpML infosets.

Observations on serialize results

On average the Fast Infoset DOM serializer (using default settings) is 25% to 30% faster than the Xerces 2.7.1 DOM XMLSerializer.

Indexing of content for less than 16 or 24 characters (instead of the default 7) can result in a small decrease in performance for infosets that contain such redundant information (but note that this is mostly offset by a larger increase in parsing performance).

For 'small' XML infosets (the UBL and FpML infosets) an external vocabulary can on average increase Fast Infoset serialization by 20% to 25% (relative to XML).

Observations on size results

On average fast infoset documents (when using default settings for serialization) are 40% to 60% smaller than XML documents.

Indexing of content for less than 16 or 24 characters (instead of the default 7) can result in good size reductions for infosets that contain such redundant information (for example the FpML infosets. Note that FpML documents were obtained from the FpML web site and have not been modified. They contain white spaces between close and open tags for readability).

For 'large' XML infosets the use of an external vocabulary makes little difference to the size of the fast infoset documents. Large GZIP'ed fast infoset documents tend to be slightly smaller than GZIP'ed XML documents, ranging from 5 to 20% smaller (relative to XML) and depending on the information document.

For 'small' XML infosets (the UBL and FpML infosets) an external vocabulary can on average reduce the size by a further 20% to 25% (relative to XML). In some cases a fast infoset document with an external vocabulary and full indexing can be smaller than the GZIP'ed XML document. The GZIP'ed fast infoset document is always smaller than the GZIP'ed XML document.

General conclusions

When parsing and size of messages is a bottle neck in a system Fast Infoset can provide a performant and interoperable solution (note that encoding algorithms can be used reduce the bottle neck on binding the binding of data types to lexical representations).

Fast Infoset is more efficient at parsing than serializing when using the DOM API (although using the encoding algorithm feature, see “Encoding Algorithms” section of this paper, can potentially improve serialization).

For the types of XML infoset being serialized and parsed it is worth investigating whether the default level of indexing provides the maximum efficiency. A larger value for the indexing of text content and attribute values can results in smaller documents that do not take much longer to serialize and are faster to parse, although this will result in more use of memory by both the parser and serializer. The methods setCharacterContentChunkSizeLimit and setAttributeValueSizeLimit on the interface FastInfosetSerializer can be used to set the indexing limits for text content and attribute values respectively.

The use of external vocabularies can be a very effective way to increase the efficiency of parsing, serializing and size at the expense of the fast infoset documents no longer being self-describing (but still self-structuring). The following scenario may be appropriate for use of external vocabularies: A protocol between clients and services communicating using small messages that are application specific in the sense that there is a fixed set of well described structures for the message.

Fast Infoset can provide modest to good compression of XML infosets, depending on what features of Fast Infoset are used. It is interesting to note that for the XML infosets tested GZIP'ed fast infoset documents created using an external vocabulary are smaller than compressed XML documents. Given that the fast infoset documents smaller than XML it may be that compressing such documents does add too much to the cost of serializing.

Further work

Add an option to perform GZIP compression for parsing and serializing.

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