Maybe first check what is using the swap?
swap-use.sh | sort -k 5,5 -n
#!/bin/bash
SUM=0
OVERALL=0
for DIR in `find /proc/ -maxdepth 1 -type d | egrep "^/proc/[0-9]"`
do
PID=`echo $DIR | cut -d / -f 3`
PROGNAME=`ps -p $PID -o comm --no-headers`
for SWAP in `grep Swap $DIR/smaps 2>/dev/null| awk '{ print $2 }'`
do
let SUM=$SUM+$SWAP
done
echo "PID=$PID - Swap used: $SUM - ($PROGNAME )"
let OVERALL=$OVERALL+$SUM
SUM=0
done
echo "Overall swap used: $OVERALL"
-----Original Message-----
From: Lincoln Bryant [mailto:lincolnb@xxxxxxxxxxxx]
Sent: dinsdag 23 januari 2018 21:13
To: Samuel Taylor Liston; ceph-users@xxxxxxxxxxxxxx
Subject: Re: OSD servers swapping despite having free
memory capacity
Hi Sam,
What happens if you just disable swap altogether? i.e., with `swapoff
-a`
--Lincoln
On Tue, 2018-01-23 at 19:54 +0000, Samuel Taylor Liston wrote:
> We have a 9 - node (16 - 8TB OSDs per node) running jewel on centos
> 7.4. The OSDs are configured with encryption. The cluster is
> accessed via two - RGWs and there are 3 - mon servers. The data pool
> is using 6+3 erasure coding.
>
> About 2 weeks ago I found two of the nine servers wedged and had to
> hard power cycle them to get them back. In this hard reboot 22 - OSDs
> came back with either a corrupted encryption or data partitions.
> These OSDs were removed and recreated, and the resultant rebalance
> moved along just fine for about a week. At the end of that week two
> different nodes were unresponsive complaining of page allocation
> failures. This is when I realized the nodes were heavy into swap.
> These nodes were configured with 64GB of RAM as a cost saving going
> against the 1GB per 1TB recommendation. We have since then doubled
> the RAM in each of the nodes giving each of them more than the 1GB per
> 1TB ratio.
>
> The issue I am running into is that these nodes are still swapping; a
> lot, and over time becoming unresponsive, or throwing page allocation
> failures. As an example, “free” will show 15GB of RAM usage (out of
> 128GB) and 32GB of swap. I have configured swappiness to 0 and and
> also turned up the vm.min_free_kbytes to 4GB to try to keep the kernel
> happy, and yet I am still filling up swap. It only occurs when the
> OSDs have mounted partitions and ceph-osd daemons active.
>
> Anyone have an idea where this swap usage might be coming from? Thanks
> for any insight,
>
> Sam Liston (sam.liston@xxxxxxxx)
> ====================================
> Center for High Performance Computing
> 155 S. 1452 E. Rm 405
> Salt Lake City, Utah 84112 (801)232-6932
> ====================================
>
>
>
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