On 08/09/2011 06:24 PM, Darren New wrote:
> On 9/8/2011 1:14, Invisible wrote:
>> No, that's exactly what the "cache coherence" protocol prevents.
>
> Sure. I'm just saying that saying "it's write-once" doesn't
> automatically mean it's thread safe in a modern multi-processor. The
> generated code actually has to take some care to tell the processor to
> flush cache lines and such.

According to the documentation I read, this is automatic. As in, the 
code doesn't have to take any explicit action at all to ensure that all 
processors see a consistent image of main memory. It's just that if 
several cores try to access the same area at once, it gets very, very slow.

>> If defies my comprehension that what Google does is actually physically
>> possible, but anyway...
>
> It kind of boggles my mind too. Just the complexity of the monitoring
> stuff is stunning, let alone actually getting work done. :-)

Apparently it's one of the monitoring and load-balancing systems they 
translated to Haskell...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message