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Memory Contention in Linux results in High CPU load (Doc ID 2170336.1)

Last updated on APRIL 29, 2020

Applies to:

Linux OS - Version Enterprise Linux 3.0 and later
Oracle Cloud Infrastructure - Version N/A and later
Linux x86-64

Symptoms

 You have been directed to this Global Customer Support (GCS) document because your symptoms and provided data match a known scenario that can result from an inefficient configuration of the memory on your 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 this GCS document was Cluster Health Monitor (CHM), OS Watcher (OSW), or ExaWatcher data.  The data leading up the 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 swap-able 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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In this Document
Symptoms
Cause
Solution
References

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