Subj : Re: What is the real costs of LOCK on x86 multiprocesor machine?
To   : comp.programming.threads
From : Joe Seigh
Date : Sat Jul 30 2005 01:43 pm

Sean Kelly wrote:
> Joe Seigh wrote:
> 
>>Statically or dynamically linked code?  The only case I
>>think you can safely get away with making LOCK optional
>>is in system dynamically linked libraries that are hardware
>>configuration specific.  I use LOCK in inlined code since it's
>>in effect statically linked and you don't know where the code
>>will eventually execute.
> 
> 
> What about testing the hardware configuration on startup and setting a
> global state flag?  Would it be worthwhile to do this and deal with the
> duplicated asm and branching it would require?
> 
Depends on whether the global state flag is in cache when you test it
and whether ia32-64 handles short conditional jumps effectively.  The
condition means the pipeline stalls until the flag can be tested.  It
should be easy to measure the overhead though.

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

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