2011-05-14 16:18:54 +00:00
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= libpsyc Performance Benchmarks =
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In this document we present the results of performance benchmarks
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of libpsyc compared with libjson-glib and libxml2.
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== Procedure ==
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We'll use typical messages from the XMPP ("stanzas" in Jabber
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2011-05-14 17:22:24 +00:00
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lingo) and compare them with equivalent JSON encodings,
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verbose and compact PSYC formats.
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2011-05-14 16:18:54 +00:00
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In some cases we will additionally compare PSYC packets to
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a more efficient XML encoding based on PSYC methods, to have
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a more accurate comparison of the actual PSYC and XML
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syntaxes, rather than the protocol structures of PSYC and XMPP.
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== The Benchmarks ==
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=== A presence packet ===
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Since presence packets are by far the dominant messaging content
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in the XMPP network, we'll start with one of them.
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2011-05-14 17:22:24 +00:00
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Here's an example from paragraph 4.4.2 of RFC 6121.
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2011-05-14 16:18:54 +00:00
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2011-05-14 17:22:24 +00:00
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{{{
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<presence from='juliet@example.com/balcony'
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to='benvolio@example.net'>
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<show>away</show>
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</presence>
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}}}
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2011-05-14 16:18:54 +00:00
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2011-05-14 17:22:24 +00:00
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And here's the same information in a JSON rendition:
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{{{
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2011-05-14 22:54:43 +00:00
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["presence",{"from":"juliet@example.com/balcony","to":"benvolio@example.net"},{"show":"away"}]
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2011-05-14 17:22:24 +00:00
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}}}
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Here's the equivalent PSYC packet in verbose form
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(since it is a multicast, the single recipients do not
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need to be mentioned):
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{{{
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:_context psyc://example.com/~juliet
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=_degree_availability 4
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_notice_presence
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}}}
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And the same in compact form:
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{{{
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:c psyc://example.com/~juliet
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=da 4
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np
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}}}
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2011-05-14 16:18:54 +00:00
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=== An average chat message ===
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{{{
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<message
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from='juliet@example.com/balcony'
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id='ktx72v49'
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to='romeo@example.net'
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type='chat'
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xml:lang='en'>
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<body>Art thou not Romeo, and a Montague?</body>
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</message>
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}}}
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=== A new status updated activity ===
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Example taken from http://onesocialweb.org/spec/1.0/osw-activities.html
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You could call this XML namespace hell:
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{{{
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<iq type='set'
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from='hamlet@denmark.lit/snsclient'
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to='hamlet@denmark.lit'
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id='osw1'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<publish node='urn:xmpp:microblog:0'>
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<item>
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<entry xmlns="http://www.w3.org/2005/Atom"
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xmlns:activity="http://activitystrea.ms/spec/1.0/"
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xmlns:osw="http://onesocialweb.org/spec/1.0/">
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<title>to be or not to be ?</title>
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<activity:verb>http://activitystrea.ms/schema/1.0/post</activity:verb>
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<activity:object>
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<activity:object-type>http://onesocialweb.org/spec/1.0/object/status</activity:object-type>
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<content type="text/plain">to be or not to be ?</content>
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</activity:object>
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<osw:acl-rule>
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<osw:acl-action permission="http://onesocialweb.org/spec/1.0/acl/permission/grant">
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http://onesocialweb.org/spec/1.0/acl/action/view
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</osw:acl-action>
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<osw:acl-subject type="http://onesocialweb.org/spec/1.0/acl/subject/everyone"/>
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</osw:acl-rule>
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</entry>
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</item>
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</publish>
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</pubsub>
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</iq>
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}}}
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http://activitystrea.ms/head/json-activity.html proposes a JSON encoding
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of this. We'll have to add a routing header to it.
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{{{
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["activity",{"from":"hamlet@denmark.lit/snsclient"},{"verb":"post",
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"title":"to be or not to be ?","object":{"type":"status",
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"content":"to be or not to be ?","contentType":"text/plain"}]
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}}}
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http://about.psyc.eu/Activity suggests a PSYC mapping for activity
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streams. Should a "status post" be considered equivalent to a presence
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description announcement or just a message in the "microblogging" channel?
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We'll use the latter here:
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{{{
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:_context psyc://denmark.lit/~hamlet#_follow
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:_subject to be or not to be ?
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:_type_content text/plain
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_message
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to be or not to be ?
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}}}
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2011-05-14 16:18:54 +00:00
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=== A message with JSON-unfriendly characters ===
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{{{
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<message
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from='romeo@example.net/orchard'
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id='sl3nx51f'
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to='juliet@example.com/balcony'
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type='chat'
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xml:lang='en'>
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<body>"Neither, fair saint, if either thee dislike.", he said.
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And
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the
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rest
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is
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history.</body>
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</message>
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}}}
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2011-05-14 16:18:54 +00:00
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=== A message with XML-unfriendly characters ===
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{{{
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<message
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from='juliet@example.com/balcony'
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id='z94nb37h'
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to='romeo@example.net'
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type='chat'
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xml:lang='en'>
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<body>Wherefore art thou, Romeo?</body>
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<body xml:lang='cs'>
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PročeŽ jsi ty, Romeo?
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</body>
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</message>
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}}}
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=== A message with PSYC-unfriendly strings ===
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{{{
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<message
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from='juliet@example.com/balcony'
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id='c8xg3nf8'
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to='romeo@example.net'
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type='chat'
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xml:lang='en'>
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<subject>I implore you with a pointless
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newline in a header variable</subject>
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<body>Wherefore art thou, Romeo?
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And for practicing purposes we added a PSYC packet delimiter.</body>
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</message>
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}}}
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2011-05-14 16:18:54 +00:00
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=== A packet containing a JPEG photograph ===
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2011-05-15 20:59:30 +00:00
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... TBD ...
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2011-05-14 17:22:24 +00:00
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=== A random data structure ===
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In this test we'll not consider XMPP at all and simply compare the
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efficiency of the three syntaxes at serializing a typical user data base
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storage information. We'll again start with XML:
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{{{
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<UserProfile>
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<Name>Silvio Berlusconi</Name>
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<JobTitle>Premier</JobTitle>
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<Country>I</Country>
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<Address>
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<Street>Via del Colosseo, 1</Street>
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<PostalCode>00100</PostalCode>
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<City>Roma</City>
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</Address>
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<Page>http://example.org</Page>
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</UserProfile>
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}}}
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In JSON this would look like this:
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{{{
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["UserProfile",{"Name":"Silvio Berlusconi","JobTitle":"Premier","Country":"I","Address":
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{"Street":"Via del Colosseo, 1","PostalCode":"00100","City":"Roma"},"Page":"http://example.org"}]
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}}}
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Here's a way to model this in PSYC:
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{{{
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:_name Silvio Berlusconi
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:_title_job Premier
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:_country I
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:_address_street Via del Colosseo, 1
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:_address_code_postal 00100
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:_address_city Roma
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:_page http://example.org
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_profile_user
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}}}
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== Conclusions ==
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2011-05-15 20:59:30 +00:00
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... TBD ...
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2011-05-14 17:22:24 +00:00
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== Criticism ==
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Are we comparing apples and oranges? Yes and no, depends on what you
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need. XML is a syntax best suited for complex structured data in
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well-defined formats - especially good for text mark-up. JSON is a syntax
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intended to hold arbitrarily structured data suitable for immediate
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inclusion in javascript source codes. The PSYC syntax is an evolved
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derivate of RFC 822, the syntax used by HTTP and E-Mail, and is therefore
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limited in the kind and depth of data structures that can be represented
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with it, but in exchange it is highly performant at doing just that.
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So it is up to you to find out which of the three formats fulfils your
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requirements the best. We use PSYC for the majority of messaging where
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JSON and XMPP aren't efficient and opaque enough, but we employ XML and
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JSON as payloads within PSYC for data that doesn't fit the PSYC model.
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For some reason all three formats are being used for messaging, although
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only PSYC was actually designed for that purpose.
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2011-05-14 22:54:43 +00:00
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== Caveats ==
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In every case we'll compare performance of parsing and re-rendering
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these messages, but consider also that the applicative processing
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of an XML DOM tree is more complicated than just accessing
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certain elements in a JSON data structure or PSYC variable
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mapping.
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For a speed check in real world conditions which also consider the
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complexity of processing incoming messages we should compare
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the performance of a chat client using the two protocols,
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for instance by using libpurple with XMPP and PSYC accounts.
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To this purpose we first need to integrate libpsyc into libpurple.
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2011-05-15 20:59:30 +00:00
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== Futures ==
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After a month of development libpsyc is already performing pretty
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well, but we presume various optimizations, like rewriting parts
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in assembler, are possible.
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