(Similar to a redit post:
https://www.reddit.com/r/LXD/comments/53l7on/how_does_lxd_manage_swap_space).
Ubuntu 16.04, LXC 2.13 running about 50 containers. System has 8G RAM and 20G
swap. From what I can tell, the containers are using lots of swap despite
having free memory.
Top output from the host:
-------------------------------
top - 05:23:24 up 15 days, 4:25, 2 users, load average: 0.29, 0.45, 0.62
Tasks: 971 total, 1 running, 970 sleeping, 0 stopped, 0 zombie
%Cpu(s): 8.9 us, 8.1 sy, 0.0 ni, 81.0 id, 0.7 wa, 0.0 hi, 1.2 si, 0.0 st
KiB Mem : 8175076 total, 284892 free, 2199792 used, 5690392 buff/cache
KiB Swap: 19737596 total, 15739612 free, 3997984 used. 3599856 avail Mem
-------------------------------
Top output from a container:
-------------------------------
top - 09:19:47 up 10 min, 0 users, load average: 0.52, 0.61, 0.70
Tasks: 17 total, 1 running, 16 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.3 us, 2.2 sy, 0.0 ni, 96.5 id, 0.0 wa, 0.0 hi, 1.0 si, 0.0 st
KiB Mem : 332800 total, 148212 free, 79524 used, 105064 buff/cache
KiB Swap: 998400 total, 867472 free, 130928 used. 148212 avail Mem
-------------------------------
The profile associated with the container:
-------------------------------
root@Container-001:/usr/local/tmp# lxc profile show WP_Default
config:
limits.cpu: "2"
limits.memory: 325MB
limits.memory.swap: "true"
raw.lxc: lxc.cgroup.memory.memsw.limit_in_bytes = 1300M
description: ""
devices:
eth0:
name: eth0
nictype: macvlan
parent: eth1.2005
type: nic
root:
path: /
pool: default
type: disk
name: WP_Default
-------------------------------
As it stands now, the host is using 4G of swap and the "kswapd0” program is
using lots of CPU. In fact, I have a cron job to clear the VM cache every
5mins (/bin/echo 1 > /proc/sys/vm/drop_caches).
Any pointers?
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