Re: Adding CPU to a unix box--added capacity.

In addition to my previous reply and to what David shared, I can
mention result of one project with our client where we did a benchmark
of CPUs migrating from double core Santa Rosa to quad core Barcelona.
Single core of Barcelona was slower (we had one of the first chips I
think... something like 1.6 or 1.8 GHz). We calculated new and old
capacity purely based on number of cores and GHz and we had 60%
increase in capacity.

We used TPC-C traffic and we did see increase of throughput on the
same level. However, TPC-C transactions are very simplistic and
usually far from real-life transactions.

On Nov 3, 2007 7:14 PM, Best, David <David.Best@xxxxxxxxxx> wrote:
>
>
> A while back we doubled the number of cpu's in a system from 2 to 4.    I
> monitored CPU usage at 5 minute intervals for the week before and the week
> after.
>
> For the 4cpu week the average CPU usage was: 26.39815
>
> For the 2cpu week the average CPU usage was: 54.78056
>
> So,  CPU usage pretty much halved which was what we expected.  However, that
> doesn't necessarily mean performance will increase by a factor of 2.  It
> depends on the application.  In this case the databases on this server were
> a mix of OLTP and Datamarts.   The OLTP databases did see an improvement but
> the datamarts didn't.  The reason is that OLTP transactions are normally
> short and sweet, so more could be processed at a given time.   In the case
> of the datamart, the refresh job didn't take advantage of multiple cpu's, so
> it still took the same amount of time to complete.
>
>  ________________________________
>
> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
> On Behalf Of Zhu,Chao
> Sent: Friday, November 02, 2007 10:32 AM
>
> To: oracle-l
> Subject: Adding CPU to a unix box--added capacity.
>
>
>
> hi,
>     Does anyone have experience on adding new CPU to a existing box, like
> upgrade from 8CPU to 16 CPU for example.
>     I am curious about two things;
> 1. How many CPU usage% drop do we expect? Like previously it is running at
> 50% CPU usage,  typically will it drop to 25%? or something like 30%? To ask
> the same question from another view, is , how much capacity we add to the
> box? 16CPU box = 1.X(?) of a 8CPU box. Assuming same archtecture/OS. (same
> cpu count server in different architecture may have different processing
> power?)
>   Would be nice if you can share with your experience (like on
> solaris/aix/hp etc). That's kind of typical server scalability.
>
> 2.   Can we say,  CPU_USED_BY_THIS_SESSION (stat in oracle) ~~
> Unix_CPU_COUNT * USER_MODE_CPU% (vmstat usr column)? I did couple of compare
> in my database, they look pretty close.
>
>     Does anyone ever thinking about have such a formular: it could be very
> fun.
> CPU_USED_BY_THIS_SESSION = X*logical_reads + Y*physical_reads + Z*sorts + A
> * executions + B * redo_size + C * Latch_Spins+ .......?
>
> by the way, anyone like the book"forecasting oracle performance"?
> --
> Regards
> Zhu Chao
> www.cnoug.org
>



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Alex Gorbachev, Oracle DBA Brewer, The Pythian Group
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