Subj : Re: sync vs. eieio on powerpc
To   : comp.programming.threads
From : Joe Seigh
Date : Mon Feb 28 2005 08:32 pm

On Mon, 28 Feb 2005 22:46:57 +0100, Alexander Terekhov <terekhov@web.de> wrote:

>
> Joe Seigh wrote:
>
> [... eieio ...]
>
> According to various sources, apart from IO space/device memory, eieio
> is nothing but bidirectional "store/store" fence. And, quoting one
> relatively recent IBM paper: "Although eieio orders stores to caching-
> enabled storage, lwsync is the preferred instruction for this purpose.
> It's recommended that eieio not be used for this purpose." Well, IIRC,
> lwsync imposes "load/load", "load/store", and "store/store" ordering.

Ok, on second reading it does look like eieio is only "store/store".
>
>> And I have no clue why the examples use isync for acquire semantics.
>

I'm guessing isync is "load/load" and "load/store".

So eieio + isync would be equivalent to the alleged lwsync.  Not
too bad, 28 nsec for both.

-- 
Joe Seigh

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