Re: Hyperthreading - Oracle license

From: Kevin Closson <>
Date: Fri, 11 Jan 2013 09:39:24 -0800 (PST)
Message-ID: <>

SMT cores should be thought of as another .3 of a core...and platform experts would do well to accept the new reality: 70 is the new 100

SMT is not a bad thing..not understanding it can be.

If I can get my head out of the foxhole without seeing tracers I actually have a blog post teed up on SMT 

The feature is called Simultaneous MultiThreading but since a thread is stalled until its peer thread stalls (all the while the OS charges each of them against their time slice over any given wall-clock period) I sort of poo-poo the use of the word simultaneous.

No war-horse here, but best to test.

 From: Rich Jesse <> To:
Sent: Thursday, January 10, 2013 2:30 PM Subject: RE: Hyperthreading - Oracle license  

Mark writes:

> Actually, a quick MOS search, and Oracle specifically recommends staying w/
> the "doubled" count for cpu_count.
> See Doc ID 289870.1

I saw that, too, and I'm calling "BS" on the lack of evidence, empirical or otherwise.  Unless it can be claimed that turning HT on gives one at or near a 100% gain in CPU power, it stands to reason that Oracle cannot consume at or near an additional 100%.  And I'm reasonably certain that no one is advocating HT as giving anywhere near another the performance of another core.

I understand that the CPU_COUNT isn't based on the raw CPU power.  Perhaps the suggestion was made *assuming* the reader would somehow magically consider recollecting system stats after turning on HT?

Call me paranoid (no, really, go ahead), but it just doesn't smell right...


Received on Fri Jan 11 2013 - 18:39:24 CET

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