Description of problem:

This is a request to add a performance tuning parameter to enable/disable the newer locking mechanism added as described in the bug report 1435663.
For example, similar to the 389-ds's nsslapd-db-deadlock-policy configuration parameter and performance trade offs.

The newer locking mechanism is related to the message
ERR - schemacompat - map rdlock: old way MAP_MONITOR_DISABLED

The issue is the IPA LDAP service can "hang" or appear as "hanged" for more than 20 seconds, in the slapi-nis plug-in , usually in scenario with "high" LDAP traffic.
This used to be a corner case in 2017, but we see more accurances of the dead locks, more chances of this to happen:
a LDAP search or mod operation acquire a slapi-nis map lock and a DB page lock
another thread does an update, holding hold DB page lock and need a slapi-nis map lock
Adding this new config knob in the plug-in could also be interpreted as a workaround to avoid a full deadlock in favor of a "long" transient slowdown.

The existing related bug reports are

bz 1724761 - Entry cache contention during base search
bz 1435663 - deadlock in modify operation with schema-compat plugin
https://pagure.io/389-ds-base/issue/50542 [CLOSED] / Entry cache contention during base search
https://bugzilla.redhat.com/1724761 [VERIFIED] [RHEL-7.9]
https://bugzilla.redhat.com/1435663 [CLOSED ERRATA] slapi-nis-0.56.0-10.el7
https://bugzilla.redhat.com/1435663#c18 - the short term solution / workaround
https://bugzilla.redhat.com/1435663#c30 - test script

Version-Release number of selected component (if applicable):

slapi-nis component for RHEL-7 and RHEL-8

How reproducible:

not trivial, not always on demand:
https://bugzilla.redhat.com/show_bug.cgi?id=1435663#c22

Steps to Reproduce:
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Actual results:

Expected results:

Additional info: