Oracle Linux: Memory Contention in Linux Results in High CPU Load (Doc ID 2170336.1)

Last updated on MARCH 17, 2024

Applies to:

Symptoms

There is a scenario that can result from an inefficient configuration of the memory on the x86_64 Linux system. The goal of this document is to explain that scenario at a simple and high level.

Generally speaking, the symptoms can include:

Poor database performance
System running out of memory or excessive swapping
Database instances cannot be started
Crucial system services failing
Basic OS commands (such as "ls" or "cd") hanging or very slow
SSH connections hanging or very slow
RAC instance evictions
RAC node reboots

The data that you provided in the Service Request (SR) that directed you to thisGlobal Customer Support (GCS) document was Cluster Health Monitor (CHM), OS Watcher (OSW), or ExaWatcher data.  The data leading up to the time of the event shows:

Low free memory
Swap usage
Kswapd listed in the top 20 processes - often within the top 5
Increasing CPU load as kswapd works harder and harder to find swapable memory for the Linux kernel.

 Here is an actual example from a recent SR:

2016_05_11_02_28_58_TopExaWatcher_hostname.dat
# Starting Time: 05/11/2016 02:28:58
# Sample Interval(s): 5

Cause

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