MongoDB Upgrade to version 8.0

Vishal_Ghodake · 2025-04-11T07:39:18.802Z

Hello Everyone,

Recently I have upgraded MongoDB Community Database from v6.0 to v8.0. And since when I login into mongo shell I am getting two warnings.

For customers running the current memory allocator, we suggest changing the contents of the following sysfsFile

We suggest setting the contents of sysfsFile to 0.

Server Details :
OS Version: RHEL 8.10
MongoDB Version Upgrade: v6.0.19 to v8.0.6 (PSS Replication Cluster)
FCV Value is still 7.0.

What does these warning indicates? and what OS values needs to be updated?
I can’t find related details on MongoDB official documentaion.

chris · 2025-04-11T17:57:42.372Z

Hi @Vishal_Ghodake

With 8.0 there is a change in memory allocator. The recommended OS setting have changed to support this.

This page give the settings and example systemd unit to set it up.

ref:
https://www.mongodb.com/docs/manual/administration/tcmalloc-performance/

Vishal_Ghodake · 2025-04-15T08:26:51.667Z

hi Chris,

Thank You for the advice.

As per my understanding, below are the only settings different in MongoDB 8.0 than earlier versions.

In MongoDB v7.0:

/sys/kernel/mm/transparent_hugepage/enabled: never
/sys/kernel/mm/transparent_hugepage/defrag: never

In MongoDB v8.0:

/sys/kernel/mm/transparent_hugepage/enabled: always
/sys/kernel/mm/transparent_hugepage/defrag: defer+madvise
/sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none: 0
/proc/sys/vm/overcommit_memory: 1

Please help me if there are any other changes required.