Re: JavaMemoryModel: a naive proposal

From: Bill Pugh (pugh@cs.umd.edu)
Date: Thu Jul 12 2001 - 12:21:04 EDT


At 1:13 AM +0200 7/11/01, Assaf Schuster wrote:
> A NAIVE PROPOSAL:
> Let the default memory model be SC. Let the compiler have an optimizing
> flag to compile the programs using (some) relaxed release/acquire
>semantics.

No, No, No. Never.

There must not be a JVM flag that changes the semantics of the VM.

Plus, SC would substantially hurt performance of JVM's on many
uniprocessors, and cripple it on SMP's. I don't think our JSR could
ever be approved if it crippled the performance of Java.

Sequential consistency is not an option for the semantics of Java.

If you want, you could write your own Java source code to Java byte
code compiler that inserted a dummy volatile write followed by a
dummy volatile read after each memory access. That would provide SC
semantics. But those semantics won't be the semantics of Java.

        Bill
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