Re: Oracle in an AIX LPAR
- From: Carol Dacko <dackoc@xxxxxxxxx>
- To: john40855@xxxxxxxxx
- Date: Wed, 4 Mar 2015 11:46:40 -0500
Hi John,
I believe the following paper gives you a better understanding on how IBM
has implement and recorded CPU utilization with AIX:
http://www-03.ibm.com/systems/resources/pwrsysperf_SMT4OnP7.pdf
And a more graphical representation on pages 15-32 in this PPT:
http://gibsonnet.net/AIX/ibm/ATS_Tech_Talk_Optimizing_POWER7_and_AIX_Update_Dec_2012.pdf
HTH!
Carol Dacko
Accenture Enkitec Group
On Wed, Mar 4, 2015 at 11:28 AM, John Smith <john40855@xxxxxxxxx> wrote:
> Talking to our system guys, my understanding is that this LPAR has 4 CPU's
> dedicated, with 2 more allowed, so it is capped at 6. NMON shows 24 CPU's
> available. As I watch nmon, we see that the first thread on each CPU is
> typically running at 50% usage or better. I see cpu 9 and 3 getting some
> usage (second thread on cpu's 3 and 4), but other than that only the first
> thread on each CPU is being used. I assume the first thread is the
> primary. SMT 4 is being used.
>
> The processes getting CPU are all oracle<SID> (LOCAL=NO), so sqlnet
> connections.
>
> On Wed, Mar 4, 2015 at 10:16 AM, Rich Jesse <
> rjoralist3@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
>> Hey John,
>>
>> > This is power7 in a dedicated LPAR.
>>
>> An LPAR is IBM's term for a VM. So, is there just one LPAR on your
>> POWER7?
>> I'd think there'd also be at least 2 more for VIOs, but that's stretching
>> my
>> knowledge limits...
>>
>> SMT also comes into play here. By default, the LPAR should be using SMT4,
>> which means that 1 virtual CPU core will be shown as 4 logical CPUs. You
>> should be able to see this in the "p" screen of nmon.
>>
>> You mentioned "1 thread per CPU". It sounds like you might be thinking of
>> Oracle on Windows? If so, Oracle doesn't run the same in Unix/Linux. The
>> background processes will be exposed as individual processes in AIX
>> instead
>> of Windows threads in a single process.
>>
>> Which Oracle process shows at 50% (e.g. using the "u" screen in nmon)?
>> That
>> could give a big clue...
>>
>> Let us know!
>>
>> Rich
>>
>> > On Wed, Mar 4, 2015 at 9:49 AM, Stefan Koehler <contact@xxxxxxxx>
>> wrote:
>> >
>> >> >> we see that Oracle appears to be using only 1 thread per CPU almost
>> all
>> >> the time.
>> >> You mean one vCPU = one thread, right? The CPU usage can also be shown
>> as
>> >> 50%, but it is not 50% in reality - it depends on the used entitlement
>> per
>> >> vCPU.
>>
>> [snip]
>>
>> --
>> //www.freelists.org/webpage/oracle-l
>>
>>
>>
>
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