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Date: Tue, 20 May 2014 10:47:28 -0400
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From: "Devon H. O'Dell" <devon.odell@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] waitfree
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2014-05-19 22:12 GMT-04:00 erik quanstrom <quanstro@quanstro.net>:
> i get a 126% difference executing lock xadd 1024*1024 times
> with no branches using cores 4-7 of a xeon e3-1230.  i'm sure it would
> be quite a bit more impressive if it were a bit easier to turn the timer
> interrupt off.

Dunno what to say. I'm not trying this on Plan 9, and I can't
reproduce your results on an i7 or an e5-2690. I'm certainly not
claiming that all pipelines, processors, and caches are equal, but
I've simply never seen this behavior. I also can't think of an
application in which one would want to execute a million consecutive
LOCK-prefixed instructions. Perhaps I just lack imagination.

--dho

> i really wish i had a four package system to play with right now.  that
> could yield some really fun numbers.  :-)
>
> - erik
>
> example run.  output core/cycles.
> ; 6.lxac
> 4 152880511
> 7 288660939
> 6 320991900
> 5 338755451
>
>