[jbosscache-dev] Fwd: Immutables.immutableSetCopy
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Message-ID: <4A8C79BF.3000103(a)redhat.com>
Date: Wed, 19 Aug 2009 17:16:31 -0500
From: Brian Stansberry <brian.stansberry(a)redhat.com>
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Subject: Immutables.immutableSetCopy
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This method looks quite inefficient for its actual usage.
A look in the IDE shows its used by UnversionedNode.getChildrenNames()
and getKeysDirect(). Those pass either a ConcurrentHashMap$KeySet, a
FastCopyHashMap$KeySet, Collections$EmptySet or
Collections$SingletonSet. The attempted optimizations (some of which
involve reflection) in immutableSetCopy can handle non of those and
eventually the HashSet copy constructor gets called.
A profiling run showed 22 invocations of UnversionedNode.getKeysDirect()
took 3,804 microseconds, of which 3,563 was in immutableSetCopy. 789 of
that was in the new HashSet(toCopy) call; the rest was basically wasted.
Any reason I shouldn't just turn this into a new HashSet(toCopy) call?
--
Brian Stansberry
Lead, AS Clustering
JBoss by Red Hat