sap_netweaver_preconfigure: Add SAP Note 2391706

herrmie commented 4 months ago

Hello, it would be great to have the SNote 2391706 (https://me.sap.com/notes/2391706/E) implement in the sap_netweaver_preconfigure, as it is a good thing to have Transparent Huge Pages on Linux disabled also for non-HANA systems.

Best regards, Steffen Herrmann

berndfinger commented 4 months ago

Hello, it would be great to have the SNote 2391706 (https://me.sap.com/notes/2391706/E) implement in the sap_netweaver_preconfigure, as it is a good thing to have Transparent Huge Pages on Linux disabled also for non-HANA systems.

Hi Steffen, Thank you for bringing this to our attention. I just discussed this topic with my colleagues from the SAP LinuxLab and got the reply that the SAP note 2391706 is just meant to provide "how to" assistance in case users want to disable THP on Linux (e.g. as required for SAP HANA).

The SAP note is not meant to advise users to disable THP on non-HANA systems nor does it provide a statement about any possible advantage of doing so.

So we should better not disable THP for SAP ABAP Platform, non-HANA, systems by default. Should we get informed by SAP at any time that disabling THP would be recommended by default, we will of course modify the role sap_netweaver_preconfigure (or even sap_general_preconfigure) accordingly. The code for this is already present and used in the role sap_hana_preconfigure.

Regards, Bernd

herrmie commented 4 months ago

Hello Bernd,

thanks for your reply. Unfortunately, there is nothing like another NetWeaver+DB script available. It’s a clear recommendation to deactivate THPs with Oracle and ASE on Linux (besides HANA): See SAP Notes

2989091 - Configured HugePages versus Transparent Huge Pages (THP) on Linux - SAP ASE 1871318 - Linux: Disable Transparent HugePages for Oracle Database

How can we handle that?

Thanks in advance

Steffen

marcelmamula commented 4 months ago

Hello @herrmie I have not seen comment about what OS you are using, but if you run sap_netweaver_preconfigure on SUSE SLES system, it will execute saptune with selected solution.

sap_hana_preconfigure_saptune_solution: "SAP-ASE" will apply ASE related SAP Notes and disabling THP is one of them.

saptune solution list

All solutions (* denotes enabled solution, O denotes override file exists for solution, C denotes custom solutions, D denotes deprecated solutions):
        BOBJ               - 941735 1771258 2578899 SAP_BOBJ 2993054 1656250
        HANA               - 941735 1771258 1868829 1980196 2578899 2684254 2382421 2534844 2993054 1656250
        MAXDB              - 941735 1771258 2578899
        NETWEAVER          - 941735 1771258 2578899 2993054 1656250 900929
        NETWEAVER+HANA     - 941735 1771258 1868829 1980196 2578899 2684254 2382421 2534844 2993054 1656250
        NETWEAVER+MAXDB    - 941735 1771258 2578899 2993054 1656250 900929
        S4HANA-APP+DB      - 941735 1771258 1868829 1980196 2578899 2684254 2382421 2534844 2993054 1656250
        S4HANA-APPSERVER   - 941735 1771258 1868829 2578899 2993054 1656250 900929
        S4HANA-DBSERVER    - 941735 1771258 1868829 1980196 2578899 2684254 2382421 2534844 2993054 1656250
 *      SAP-ASE            - 941735 1680803 1771258 2578899 2993054 1656250

Remember: if you wish to automatically activate the solution's tuning options after a reboot, you must enable and start saptune.service by running:
    saptune service enablestart

herrmie commented 3 months ago

Hello @marcelmamula, we are using RHEL.

Best regards, Steffen

sean-freeman commented 3 months ago

@herrmie Having a look myself, it certainly seems subjective.

Disable of `Transparent` Huge Pages, Enable of "Normal" Huge Pages....

sapsysinfo.sh in 618104 - "sapsysinfo" - Collecting system information on Linux only contains a check for Transparent Huge Pages; no warnings just a status.

Solved already?

Heavily abbreviated statement in SNote 1310037 - SUSE LINUX Enterprise Server 11: Installation notes....

Problem: On systems with large memory, frequent access to the
Translation Lookaside Buffer (TLB) may slow down the system significantly.
....
Transparent huge pages thus are of most use on systems with
very large (128GB or more) memory, and help to drive performance.
....
There are cases where THP may regress performance,
particularly when under memory pressure due to pages
being reclaimed in an effort to promote to huge pages.
....
Symptom: When you are running into the THP performance problem,
you often can see peaks in the cpu usage and a very high value of
system time (sys-time) in relation to the user time (usr-time).

Solution 1: Update your linux kernel to at least version 3.0.80-0.5.1 (SP2).
In this case Solution 2 is not needed any more.

Solution 2: If necessary, THP can be disabled....

Heavily abbreviated statement in SNote 2193512 - BWA: New alert to check if the Linux feature "Transparent Hugepages" is enabled?....

With kernel >= 3.0.80-0.5.1 a fix for the hanging situation has been provided by SUSE for SLES 11 SP2.
With this kernel version it is not necessary anymore to disable the transparent hugepages.
We strongly recommend to upgrade to kernel 3.0.93 or better as soon as possible.

Using Red Hat Enterprise Linux the fix is provided by upgrading to RHEL 7.

Nethertheless we propose to disable the Transparent Huge Pages in any case,
even on kernel >= 3.0.80, to avoid possible performance degration in BWA or TREX.

herrmie commented 3 months ago

Hello,

@sean-freeman, thanks a lot for the summarize. But we are only focusing on Transparent Huge pages. And there is the Note for ASE which stated it correctly to disable THP: https://me.sap.com/notes/2989091/E

Also for Oracle should THP be disabled, you can see it in note https://me.sap.com/notes/1871318/E and in the Oracle documentation: https://docs.oracle.com/en/database/oracle/oracle-database/19/ladbi/disabling-transparent-hugepages.html

For us, it is clear, there need to be a correction of the code with regards to disable THP on Oracle, ASE and HANA as well (which is already there) which are running on Linux. "The use of THP is not recommended for ASE (and in general not for hosts running a DBMS)." (https://me.sap.com/notes/2989091/E)

Best regards, Steffen Herrmann

sap-linuxlab / community.sap_install