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MaxCPUs and DBANALYZER

CLOEFFLER
Participant
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Hi Everyone,

We are running a new productive system with 4 Intel E5-4640 CPUs

providing 64 CPUs (32 CPUs with Hyperthreading activated).

I've made a DBANALYZER-Check which keeps complaining

parameter MaxCPUs:

'MaxCPUs' (24) exceeds number of physical CPUs (4)!

I'm now a little bit confused because I do not think that it's the best

way to configure "physical" instead of "logical CPUs".

Now: What's the right configuration if this server is a central instance?

By the way: I'm using the latest dbanalyzer_InstanceParameterCheck.cfg

download from SAP Note.

Thanks in advance.

Kind Regards,

Carsten Loeffler

Accepted Solutions (0)

Answers (1)

Answers (1)

thorsten_zielke
Contributor
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Hello Carsten,

please let me know which database version you are using and if the Analyzer message is labeled as 'info' or 'warning' or has no preceeding indicator at all.


We will probably change the message text somewhat. It originates from the early times of hyperthreading and multi core CPUs when using more logical CPUs than physical CPU cores could lead to a performance bottleneck - (edit 1)of course times have changed since...


Edit 2:
ok, I have to clarify this a bit. We still write a 'I' type info when the number of physical cores is below your usable MaxCPUs value. This is, because hyperthreading might have some negativ impact on some OS platforms and CPU types.
But this is only marked as 'I', so not warning.

Regarding your case there are two things we will change:

1. The exclamation mark '!' at the end of the line is not necessary, because it might imply that some user action is needed. So we make this message line less 'complaining' 🙂

2. This message should not have appeared at all, because is is supposed to apply to the total of physical cores only, which in your case is 32 (4 physical CPUs with 8 physical cores each). So it seems that the info message is wrongly based on the 4 physical CPUs).

I will get back to you once I have news - we will investigate this...

Thorsten

Message was edited by: Thorsten Zielke

CLOEFFLER
Participant
0 Kudos

Hi Thorsten,

thanks for your reply. It's MaxDB 7.8.02.40 running on Windows 2008 R2.

The message is labeled as "General Checks" and it looks like this (see

attached image as well)

*  I  General checks:

*  I  ---------------

*  I  'MaxCPUs' (24) exceeds number of physical CPUs (4)!

*  I  Log queue overflows: 16519, configured log queue pages: 400 for each of 24 log queues

* W1  Lock list escalations: 20, current value for parameter 'MaxSQLLocks': 900000

*  I  Servertask distribution 'EnableMultipleServerTaskUKT': NO, 'DedicatedServerTaskUKTs': YES

Kind Regards,

Carsten Loeffler

thorsten_zielke
Contributor
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Hi Carsten,

please see my info above, I have edited my last reply - as it seems the info message should not appear at all, since it is supposed to be comparing the CPU cores (32) against MaxCPU instead of the 4 physical CPUs.

Thorsten

CLOEFFLER
Participant
0 Kudos

Hi Thorsten,

thanks a lot. I'll keep an eye on the post.

Kind Regards,

Carsten