oracle SE very slow on P7

nonor73

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Jan 29, 2012, 6:20:30 AM1/29/12

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hello

We move our JDE production DB, oracle 10GR2 EE, from IBM P570 with P6
processor (4.2Ghz) on P740 with P7 processor (3.3Ghz). The first test
we ran was an import mono process, on P740 it take two time than on
P570, the import spent a lot of time in index build ans statistics
computation.
It seems that the multi-threading of P7 is not used when Oracle is used
in mono-thread, and the performance of one thread on P7 is by far less
good than P6.
If someone get some experience on Oracle on P7, could you share..

Thank you

Mladen Gogala

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Jan 29, 2012, 12:49:15 PM1/29/12

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I would think that this problem is an AIX problem, not an Oracle problem.
Oracle on Unix uses processes, not threads. The most significant
advantage of P7 over P6 is the multi-core design, capable of 8 cores, if
I remember correctly, per CPU. With multi-core CPU solutions, there is
one significant problem: the efficiency of CPU cache. The rule is simple:
the more cores you have - less efficient the cache gets, because the
cache will get flushed so frequently that it's essentially useless.
Without the advantage of multithreading, your shining P7 is actually
quite a bit slower than P6, because of the frequency.
I am aware of the fact that each core has its own 32k+32k instruction and
data L1 cache, but there is a logical problem with that: caches have to
be coherent. When a core modifies location in memory, all other cores
have to check whether they have this location in their L1/L2 caches and
flush that cache line or the entire cache, that depends on the
implementation) and re-read it. I imagine that the impact of a software
like oracle which uses shared memory and is written to exploit the
locality of references (meaning that at one point in time oracle
processes do their best to stay within the small range of addresses) on
the CPU caches can be quite severe.
You should monitor the CPU consumption with sar and see how much time
does the machine spend in the kernel mode. If the average is above 10%,
than the AIX is responsible for your slowdown, not Oracle.

--
http://mgogala.byethost5.com

Noons

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Jan 29, 2012, 8:38:08 PM1/29/12

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To add to Mladen's already very good reply, consider the following:

- P7 is a new architecture for Aix that is fully supported by Aix only
on release 7.1 onward.
- 10gr2EE is *not* certified for Aix 7.1 - and it actually needs a
patch to run correctly in 6.1.

I'd consider upgrading to 11gr2(SE/EE) as that has full support for
Aix 7.1 and hence for P7.

nonor73

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Jan 31, 2012, 5:10:27 AM1/31/12

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Hello

Thank you for your answers, yes we are on AIX 6.1 and it is possible
that oracle 10g does not use the full potential of P7, i'm afraid that
we can't migrate to AIX 7.1.
I will investigate with IBM, it's seems that downgrading the P7 from 4
threads to one could improve perfs.

Thank you

John Hurley

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Feb 1, 2012, 9:12:44 PM2/1/12

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Oracle standard edition does not do many things in parallel ... versus
enterprise edition.

Make sure you are comparing oranges to oranges ...

Mladen Gogala

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Feb 1, 2012, 9:57:39 PM2/1/12

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John, the original poster specified "oracle 10GR2 EE". I don't thing that
SE is the problem here.

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http://mgogala.byethost5.com

John Hurley

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Feb 4, 2012, 7:01:50 PM2/4/12

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Mladen:

# John, the original poster specified "oracle 10GR2 EE". I don't thing

that SE is the problem here.

The subject line from op says "Oracle SE very slow on P7" and as far
as I know SE <> EE ...