Performance Issues with MAXCPU

[Former Member]

Hello,

we are currently using MaxDB 7.6.03.07 and would like to migrate it to a new (faster) server.

On the old server MAXCPU is set to 1.

On the new server if MAXCPU=1 then the performance is good.

If I set MAXCPU=4 on the new server then the performance is bad for some queries. There are differences about 10sec or more.

Can you please give me some hints, how to use the MAXCPU Parameter correctly?

Are there any other parameters which have to be changed too?

Many thanks in advance.

[former_member524429 · Accepted solution]

Hi,

On which OS your new (faster) server is running ?

Have you monitored the CPU load at the time of performance issue for some queries as u have mentioned ?

Any other application is there on that new server which is consuming CPU or any other resources ?

Please share the existing value of the following parameters :

HIRES_TIMER_TYPE ? (= CPU or GETTIMEOFDAY )

TASKCLUSTER02 ? (= 1 )

MAXUSERTASKS ?

Also look at the point "Which factors determine how the MAXCPU parameter is set?" of SAP Note 936058 - FAQ: SAP MaxDB Runtime Environment to get more information.

Regards,

Bhavik G. Shroff

[Former Member · Accepted solution]

Hi,

Thank you for your answer.

The new Server is Ubuntu Linux 10.04.

It has 2 CPUs with 4 cores.

The CPU usage on the system is vere low, almost 0%.

If I run the query the cpu usage is 1% for the kernel task.

HIRES_TIMER_TYPE = CPU

TASKCLUSTER02 ? = ti,100dw;13us;

MAXUSERTASKS = 50

I have open only one connection to the db.

[former_member524429 · Accepted solution]

Hi,

As per SAP Note 1006491 - MaxDB on Linux (NUMA): Performance problems with MAXCPU > 1, you can set HIRES_TIMER_TYPE parameter value from CPU to GETTIMEOFDAY.

As per SAP Note 425051 - liveCache performance problems with MAXCPU greater than 1, you can try with MAXCPU=1 and parameter TASKCLUSTER02 with ...,1*us; value.

Also refer SAP Note 936058 - FAQ: SAP MaxDB Runtime Environment && SAP Note 1173395 - FAQ: MaxDB configuration to get more information.

Regards,

Bhavik G. Shroff

[Former Member · Accepted solution]

Hi,

Thank you for your answer.

I will try this settings.

Unfortunately I don't have an smp account, so I am not able to read them.

I could not find these notes in the public wiki.

Do these note some day appear in the public wiki?

[Former Member · Accepted solution]

Hi,

setting HIRES_TIMER_TYPE = GETTIMEOFDAY did it !!!

[simon_matter · Accepted solution]

We are running 7.7.06.09 on RHEL5/x86_64 on AMD CPUs and I'm wondering if we also should change HighResolutionTimer? Users of MaxDB in non SAP environments can usually not access SAP Notes which is really sad because we just can't access important information sometimes. Any chance we can learn what "SAP Note 1006491 - MaxDB on Linux (NUMA): Performance problems with MAXCPU > 1" says exactly?

Thanks,

Simon

[Former Member · Accepted solution]

Hi,

Our new server has also AMD Opteron CPUs. May be this information helps you.

We descided on mid term to migrate to another database (Postgres or MySQL).

It is really sad that there are two worlds, the community and the sap world.

The community doesn't get the same information and versions as the sap world.

For example you can not even read the change/release-notes if you don't have an smp account.

[simon_matter · Accepted solution]

Thanks for the clarification, when I read NUMA I just thought "doesn't AMD Opteron based server count as NUMA arch"? So yes, it seems we may also be affected - or the issue has been resolved in our version. If the issue is still there in our version, we might have the problem too but don't know it.

As you correctly stated, while MaxDB is an excellent product also for non SAP environments, it's sometimes the lack of access to information which makes our life harder than needed.

[simon_matter · Accepted solution]

Could someone post "SAP Note 1006491" here, please?

Thanks,

Simon

[former_member276520 · Accepted solution]

You can read release notes (although in great detail so it's difficult to see which are important) at http://maxdb.sap.com/webpts -> My Release Notes.

br,

Sebastian