RFR: 8006593: Performance and compatibility improvements to hash based Map implementations

[Mike Duigou]

Unfortunately, this change doesn't fix 8006593. We do have a fix planned for 8006593 in Java 8 but there's a difficulty in the current implementation that means we can't detect if the SecurityManager is initialized. The VM.isBooted() check is insufficient. 

Mike

On Mar 5 2013, at 06:53 , Salter, Thomas A wrote:

> Will this change do anything to fix: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8002283?
> 
> --------------------
> Date: Mon, 4 Mar 2013 12:21:08 -0800
> From: Mike Duigou <mike.duigou at oracle.com>
> Subject: RFR: 8006593: Performance and compatibility improvements to
> 	hash	based Map implementations
> To: "core-libs-dev at openjdk.java.net Libs"
> 	<core-libs-dev at openjdk.java.net>
> Message-ID: <79A5A703-12DA-4C66-94F7-34534761D217 at oracle.com>
> Content-Type: text/plain; charset=us-ascii
> 
> Hello all;
> 
> The alternative hashing implementation introduced in 7u6 added an unfortunate bottleneck to the initialization of HashMap and Hashtable instances. This patch avoids the performance bottleneck of using a shared Random instance by using a ThreadLocalRandom instead.
> 
> Along with this change are some additional performance improvements to further reduce the overhead of the alternative hashing feature and generally improve the performance of Hashtable or HashMap.
> 
> http://cr.openjdk.java.net/~mduigou/JDK-8006593/3/webrev/
> 
> Once review is completed here this patch will be proposed to JDK7u-dev for integration into the next 7u performance/feature release.
> 
> Mike
>