Re: Merging relayfs?

[Richard J Moore]

Tom Zanussi <zanussi@xxxxxxxxxx> wrote on 14/07/2005 16:01:25:


> The only things that are atomic are the counts of produced and
> consumed buffers and these are only ever updated or read in the slow
> buffer-switch path.  They're atomic because if they weren't, wouldn't
> it be possible for the client to read an unfinished value if the
> producer was in the middle of updating it?


This depends on architecture.  It is possible under some architectures to
see the so-called score-boarding effect when reading on one processor while
writing on another when not having imposed any atomicity. From memory, I
believe this might be possible with zSeries, but I'll need to check the
microarchitecture docs. It's been a long time since I read them but I do
recall a reference to the score-boarding effect.


>  ...


Richard


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Richard J Moore
IBM Advanced Linux Response Team - Linux Technology Centre
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