Memory allocation stuck when using TMPFS/RAMFS on Linux

Troubleshooting

Problem

On Linux systems with Non-Uniform Memory Access (NUMA) support, when a Temporary File Storage (tmpfs) or Random Access Memory File Storage (ramfs) is setup and using memory, processes may encounter severe delays in processing memory allocation requests.For example, memory intensive programs that request a large memory allocation will process for a long time (15 - 30+ minutes).

Resolving The Problem

Source

RETAIN tip: H195156

Issue

For example, memory intensive programs that request a large memory allocation will process for a long time (15 - 30+ minutes).

Affected configurations

The system may be any of the following IBM servers:

System x3800, Type 8865, any model
System x3850 M2, Type 7141, any model
System x3850 M2, Type 7144, any model
System x3850 M2, Type 7233, any model
System x3850 M2, Type 7234, any model
System x3850, Type 8863, any model
System x3850, Type 8864, any model
System x3950 E, Type 8874, any model
System x3950 E, Type 8879, any model
System x3950 M2, Type 7141, any model
System x3950 M2, Type 7144, any model
System x3950 M2, Type 7233, any model
System x3950 M2, Type 7234, any model
System x3950, Type 8872, any model
System x3950, Type 8878, any model
iDataPlex dx360 M2 Server, Type 6380, any model
iDataPlex dx360 M2 Server, Type 7321, any model
iDataPlex dx360 M2 Server, Type 7323, any model

This tip is not option specific.

The system is configured with at least one of the following:

Red Hat Enterprise Linux 5, Update 3

Note: This does not imply that the network operating system will work under all combinations of hardware and software.

Please see the compatibility page for more information:

	http://www.ibm.com/servers/eserver/serverproven/compat/us/

Workaround

Disable NUMA zone reclaim for Linux kernel by typing the following command:

	sysctl vm.zone_reclaim_mode=0

This command takes effect immediately and does not require a reboot.

To have this setting permanently in effect, add the following line to file /etc/sysctl.conf:

	vm.zone_reclaim_mode=0

This setting takes effect upon each subsequent reboot.

Additional information

The NUMA memory allocation behavior is a limitation on newer Linux kernels and may occur on any NUMA system with the numa zone reclaim mode triggered (zone_reclaim_mode=1).

This issue appears in the Linux kernel. There is no fix at this time.

Document Location

Worldwide

Operating System

System x:Operating system independent / None

Applicable countries and regions

Worldwide

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Document Information

More support for:
System x->System x3800

Document number:
855156

Modified date:
29 January 2019

UID

ibm1MIGR-5079940

IBM Support

Tips

Memory allocation stuck when using TMPFS/RAMFS on Linux - IBM Servers