Hi,
I have a smiliar problem on a CentOS 6.4 KVM host.
The host has 32 GB memory.
virt-top shows: Mem: 30208 MB (30208 MB by guests)
vm.swappiness = 0
Guests couldn't use more than 30,2 GB memory!
# uname -r
2.6.32-358.14.1.el6.x86_64
# uptime
13:48:16 up 132 days, 1:55, 3 users, load average: 3.10, 2.45, 1.16
# sysctl vm.swappiness
vm.swappiness = 0
# free -m
total used free shared buffers cached
Mem: 32081 31784 296 0 206 2635
-/+ buffers/cache: 28943 3137
Swap: 16111 3220 12891
Swap usage:
PID=1877 swapped 415092 KB (qemu-kvm)
PID=1925 swapped 47680 KB (qemu-kvm)
PID=2012 swapped 37188 KB (qemu-kvm)
PID=2114 swapped 555560 KB (qemu-kvm)
PID=2154 swapped 191832 KB (qemu-kvm)
PID=5299 swapped 341108 KB (qemu-kvm)
PID=11564 swapped 327620 KB (qemu-kvm)
PID=15383 swapped 218360 KB (qemu-kvm)
PID=16299 swapped 11280 KB (qemu-kvm)
PID=20391 swapped 946656 KB (qemu-kvm)
PID=30963 swapped 23040 KB (qemu-kvm)
PID=31248 swapped 169680 KB (qemu-kvm)
Overall swap used: 3285096 KB
What's going wrong? vm.swappiness ist set to 0 and the system has enough
free memory without need of swapping?
--
Chris
2013/12/12 Devin Reade <gdr at gno.org>
> --On Tuesday, December 10, 2013 08:18:09 AM -0800 John R Pierce
> <pierce at hogranch.com> wrote:
>
> > during idle time, dirty pages will be written to swap so they can then
> > be discarded if needed. ignore it, it means nothing
>
> Agreed. If you want to see if paging is actually an issue,
> run "vmstat -5" and ignore the first line of output. If, over time,
> you're seeing consistently high values for the si and so columns,
> then you have something to investigate. If they're usually
> low or zero, then ignore your swap usage.
>
> Same thing goes for the "free" values in top and vmstat; having
> low free memory counts in a long running kernel is normal and
> can be ignored. (Too many people, especially coming from the
> windows world, get wrapped around the handle about this.)
>
> If you want to maintain a historical record of memory and other
> performance indicators that you can use for investigative purposes
> after the fact, see the man page for sar(1).
>
> Devin
>
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