RFR: 8006593: Performance and compatibility improvements to hash based Map implementations (original) (raw)

Mike Duigou mike.duigou at oracle.com
Tue Mar 5 17:24:40 UTC 2013

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/viewbug.do?bugid=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

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