High kswapd - Mailing list pgsql-performance

From Don Seiler
Subject High kswapd
Date
Msg-id CAHJZqBCWEk6-0NG9bQ8XWRaRz97ppPh=ZZZ89Ykvkn+EUHSNcg@mail.gmail.com
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Responses Re: High kswapd
List pgsql-performance
Good morning,

Ubuntu 16.04.6 LTS
PostgreSQL 9.6.5

On one of our database servers, we're regularly seeing kswapd at the top of "top" output, regularly using over 50 %CPU. We should have well over 80GB of available memory according to "free -m".

# free -m
              total        used        free      shared  buff/cache   available
Mem:         125910       41654         820         857       83435       82231
Swap:           511         448          63

We've already got vm.swappiness and vm.zone_reclaim_mode set to 0, and NUMA is disabled from what I can see:

# dmesg | grep -i numa
[    0.000000] No NUMA configuration found


We are using HugePages and things look good there as well. Curious what would be causing kswapd to run hot like it is, or if it is a red herring as I look into high CPU usage on this box (although, again, it is the single-highest CPU user).

--
Don Seiler
www.seiler.us

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