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Disable Transparent Huge Pages (THP)
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Transparent Huge Pages (THP) is a Linux memory management system that reduces the overhead of Translation Lookaside Buffer (TLB) lookups on machines with large amounts of memory by using larger memory pages.
However, database workloads often perform poorly with THP enabled, because they tend to have sparse rather than contiguous memory access patterns. When running MongoDB on Linux, THP should be disabled for best performance.
To ensure that THP is disabled before mongod
starts,
you should create a service file for your platform's initialization
system that disables THP at boot. Instructions are provided below for
both the systemd and the System V init initialization systems.
Additionally, for RHEL / CentOS
systems that make use of ktune
and tuned
performance profiles,
you must create a custom tuned
profile as well.
Create a Service File
To create a service file that disables THP, you will use the
built-in initialization system for your platform. Recent versions
of Linux tend to use systemd (which uses the systemctl
command),
while older versions of Linux tend to use System V init (which uses
the service
command). Refer to the documentation for your operating
system for more information.
Use the initialization system appropriate for your platform:
Using tuned
and ktune
Important
If using tuned
or ktune
, you must also perform the steps in
this section after creating the service file above.
tuned
and ktune
are dynamic kernel tuning tools that can affect
the transparent huge pages setting on your system. If you are using
tuned
/ ktune
on your RHEL
/ CentOS system while running mongod
, you must create a custom
tuned
profile to ensure that THP remains disabled.