RE: cas latch
- From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>
- To: <kaygopal@xxxxxxxxx>, <exriscer@xxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 30 Oct 2006 12:34:24 -0500
As K Gopalakrishnan mentioned, CAS latch is "Compare and Swap". My
understanding is that, on *most* modern CPUs, the CAS instruction is
built-in to the instruction set as an atomic operation. In those cases,
you shouldn't see CAS latch used at all, cause Oracle can directly use
the CAS instruction itself. In cases where the CPU does not support a
CAS instruction, Oracle has implemented the CAS functionality in
software. To support the atomicity of the CAS functionality in
software, the CAS latch is utilized.
-Mark
--
Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning
There is nothing so useless as doing efficiently that which shouldn't be
done at all. -Peter F. Drucker, 1909-2005
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of K Gopalakrishnan
Sent: Monday, October 30, 2006 12:17 PM
To: exriscer@xxxxxxxxx; oracle-l
Subject: Re: cas latch
Cheng,
Do you see any contention for this latch?
CAS is Compare and Select. Check
http://en.wikipedia.org/wiki/Compare_and_swap for some details on CAS.
Have a nice day !!
------------------------------------------------------------
Best Regards,
K Gopalakrishnan,
Co-Author: Oracle Wait Interface: Oracle Press 2004.
http://www.amazon.com/gp/product/007222729X/
Author: Oracle Database 10g RAC Handbook, Oracle Press 2006
http://www.amazon.com/gp/product/007146509X/
----- Original Message ----
From: LS Cheng <exriscer@xxxxxxxxx>
To: oracle-l <oracle-l@xxxxxxxxxxxxx>
Sent: Monday, 30 October, 2006 8:43:47 AM
Subject: cas latch
Hi
I was wondering if anyone know what does cas latch do? I know is a
shared latch but not sure for what part of SGA?
Thanks
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