[concurrency-interest] Java Memory Model versus dotnet Memory Model

Jeremy Manson jmanson at cs.purdue.edu
Thu Nov 3 11:57:23 EST 2005


Osvaldo Pinali Doederlein wrote:
> Hi,
> 
> This excellent post (from Microsoft's JIT program manager) is a very
> good overview of this issue:
> 
> http://discuss.develop.com/archives/wa.exe?A2=ind0203B&L=DOTNET&P=R375
> 
> Go straight to "CAVEATS for V1" in the end.  Basically, it seems that
> Microsoft gets away with a weak MM and implementation, because they
> support mostly the P5/P6 platform which hardware MM is very strong.
> So they can use all compiler optimizations they want without issues.
> But IIRC the Intanium is not as nice as the Pentium, so I'd expect
> MS to have improved this in .NET 2.0 which supports 64-bit platforms.
> 
> A+
> Osvaldo
> 

I'm not sure how excellent this article is.  For example, his LazyInit 
example ignores reordering by the reader.  Even with the rules he 
states, you would really need a memory barrier before the first read of 
the singleton.

Having said that, the post is 3 years old and describes the ECMA 
standard, which we know they are ignoring.  So it may not be all that 
useful in understanding what they are doing now.

					Jeremy


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