Re: JavaMemoryModel: deleting dead volatile ref's

From: Cliff Click (cliff.click@sun.com)
Date: Sun Jul 14 2002 - 22:56:25 EDT

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Hey, no problem! It stays - for now. ;-)

Sometime Real Soon Now (but alas, probably not by the 1.4.2 release)
I intend to attempt to remove unneeded synchronization, nested locks
& the like. It's gonna be a bumpy ride! :-)

Cliff

David Holmes wrote:
> Cliff Click wrote:
>>If I see a dead volatile load I can remove the actual load, but
>>a volatile ref includes a 'MemBarAcquire' (in HotSpot parlance)
>>to help prevent various compiler & hardware reorderings. Can I
>>remove the MemBarAcquire as well?
>
> If I understand you right - NO! :) The use of a 'dummy' access to a
> volatile is often used purely for the memory affects. I have a
> hashtable-like data structure that allows concurrent read access without
> locks. A 'dead' read of a volatile is used to ensure fresh loads of the data
> variables.

-- Dr. Cliff Click Chief Architect, HotSpot Server Sun Microsystems, Inc. Cliff.Click@Sun.COM Senior Staff Engineer 4150 Network Circle (408) 276-7046 MS USCA14-102 Santa Clara, CA 95054

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