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CentOS 6 vs 7 Swapiness

CentOS 6 vs 7 Swapiness

Contributor

This is a crosspost from cdh-user mailinglist, sorry if this is any inconveniance.

 

We've been running CDH5.12 with CentOS 6.x with no problems using vm.swapiness=1 setting. Recently we've updated to CentOS7.4 and using the same system parameters we did before, we now we see constant warnings in CM of swap beng above thresholds. After monitoring this for a few days we see both >100 pages in last 5m warnings as well as swap space used increasing above 250MB, our of 4G available.

 

We run 256Gig RAM nodes which never use more than 230G subscription(all processes). We see swap behaviour even though the system itself is reporting 80G/256 used. We're running all recommendations in: https://www.cloudera.com/documentation/enterprise/5-12-x/topics/cdh_admin_performance.html, including turning off the 'tuned' service. 

 

Since these are warnings in CM, I assume this is undesired behaviour, but at the same time Centos7 seems to handle swapping differently. Any recommendations for CentOS7 specifically?