SAP HANA DB raises a High alert about transparent huge pages kernel parameter not being set to “never”

SUSE Linux Enterprise Server for SAP applications 15 SP6

SUSE Linux Enterprise Server for SAP applications 15 SP5

When saptune solution such as HANA or S4HANA-DBSERVER is applied, SAP HANA DB raises an alert about THP being activated.

Identifying the currently applied saptune solution:

# saptune status

saptune.service:          enabled/active
saptune package:          '3.1.4'
configured version:       '3'
enabled Solution:         S4HANA-DBSERVER (941735, 1771258, 1868829, 1980196, 2578899, 2684254, 2382421, 2534844, 2993054, 1656250)
applied Solution:         S4HANA-DBSERVER (941735, 1771258, 1868829, 1980196, 2578899, 2684254, 2382421, 2534844, 2993054, 1656250)
additional enabled Notes: 
enabled Notes:            941735 1771258 1868829 1980196 2578899 2382421 2534844 2993054 1656250 2684254
applied Notes:            941735 1771258 1868829 1980196 2578899 2382421 2534844 2993054 1656250 2684254
staging:                  disabled
staged Notes:             
staged Solutions:         

sapconf.service:          disabled/inactive
tuned.service:            disabled/inactive
systemd system state:     running
virtualization:           microsoft
tuning:                   compliant

Checking THP setting:

 # saptune solution verify S4HANA-DBSERVER

(shortened for brevity)

SAPNote, Version | Parameter                          | Expected                    | Override  | Actual                      | Compliant
.
.
2684254, 24     	 | THP                       	         | madvise                     |                 | madvise                  | yes
.	
.

The system is shown as being tuned correctly for the applied solution. Despite this, HANA DB complains about THP setting being incorrect.

According to SAP note 2684254, THP setting for SLES 15 SP5 and higher has changed from never to madvise. This change is reflected in the saptune package changelog:

* With SAP Note 2684254 updated to Version 24 the setting of
    transparent hugepages (THP) will change from 'never' to
    'madvise' for systems running 15SP5 and higher.

When a HANA-specific saptune solution (such as HANA or S4HANA-DBSERVER) is applied, the setting can be verified by:

# cat /sys/kernel/mm/transparent_hugepage/enabled
always [madvise] never

This is the correct and recommended setting. However, some HANA DB versions might still display an alert, demanding the older never setting. This will be corrected in the future.

As of SLES 15 SP5, the recommended setting for THP is madvise. Some HANA DB versions do not reflect this update yet.

SAP Note 2684254 - SAP HANA DB: Recommended OS settings for SLES 15 / SLES for SAP Applications 15

SAP Note 2131662 - Transparent Huge Pages (THP) on SAP HANA Servers

If the customer for whatever reason chooses to use the older THP setting of never, it can be accomplished by customising the corresponding SAP note (2684254).

# saptune note customise 2684254

this will open the SAP note in a vi editor. Remove everything in the file and leave only the following content:

[vm]
# Disable transparent hugepages (THP)
# changes /sys/kernel/mm/transparent_hugepage/enabled
# 'never' to disable, 'always' to enable
# SAP Note 2131662, 2031375
#
THP=never

Save the file. This will put the file in /etc/saptune/override where its content can be checked later.

# saptune note revert 2684254 

# saptune note apply 2684254

# saptune solution verify

(shortened for brevity)

SAPNote, Version | Parameter                          | Expected                    | Override  | Actual                      | Compliant
.
.
2684254, 24      	    | THP    	                              | never                          | never      | never                        | yes
.

In the THP row, it should now show the Expected and Actual values as never (and also the Override value is now never, since the original note's setting of madvise has been overriden by the customisation.