Op 05-09-11 18:54, Thomas Goirand schreef:
On 09/05/2011 06:48 PM, Wiebe Cazemier wrote:
Package: xen-hypervisor-4.0-amd64
Version: 4.0.1-2
Severity: normal
Tags: upstream
When creating Xen DomU's, at some point xend invokes the oom-killer and
the entire machine restarts:
Sep 5 12:04:59 arbiter kernel: [259697.101212] __ratelimit: 136
callbacks suppressed
Sep 5 12:04:59 arbiter kernel: [259697.101218] xend invoked oom-killer:
gfp_mask=0x200da, order=0, oom_adj=0
Sep 5 12:04:59 arbiter kernel: [259697.101225] xend cpuset=/
mems_allowed=0
Sep 5 12:04:59 arbiter kernel: [259697.101230] Pid: 1841, comm: xend
Not tainted 2.6.32-5-xen-amd64 #1
Sep 5 12:06:23 arbiter kernel: imklog 4.6.4, log source = /proc/kmsg
started.
Sep 5 12:06:23 arbiter rsyslogd: [origin software="rsyslogd"
swVersion="4.6.4" x-pid="1409" x-info="http://www.rsyslog.com";]
(re)start
Sep 5 12:06:23 arbiter kernel: [ 0.000000] Initializing cgroup
subsys cpuset
xm info says the machine has 10231 MB of RAM. These are the VMs that
normally run:
Name ID Mem VCPUs State Time(s)
Domain-0 0 2177 1 r----- 127.1
one 1 1536 2 r----- 192.4
two 2 512 1 -b---- 2.7
three 3 1024 1 -b---- 188.6
four 4 512 1 -b---- 12.7
five 5 2048 2 -b---- 151.7
six 6 1024 2 r----- 64.9
seven 7 1024 2 -b---- 65.9
eight 8 1024 2 -b---- 100.7
Funny domU names! :)
Well, I actually obfuscated the names. Personally, I don't mind revealing such
things, but I don't know what 'the company' would say...
That means 8704 MB of memory is used.
Over the last couple of days, I've experienced that when creating two
VM's with 512 MB RAM, the oom-killer is invoked. This should not happen
because Dom0 can shrink and because the machine should not restart when
it is out of memory.
This is a production Xen host, which is becomming a liability, because
it's so unpredictable.
Current Dom0 kernel: Linux arbiter 2.6.32-5-xen-amd64
Hi,
I wouldn't recommend to just let your dom0 shrink. Set it directly to a
much lower memory footprint, something like 512 MB of RAM, so that the
Linux kernel sees directly that it doesn't have so much memory to deal
with, and it will not allocate too big buffers and so on. Here's how to
do this with the Squeeze grub:
echo "
# Start dom0 with less RAM
GRUB_CMDLINE_XEN_DEFAULT=\"dom0_mem=512M\"
">>/etc/default/grub
Then either run update-grub2 or dpkg-reconfigure grub-pc (and of course
reboot...). If you do that, I'm sure your troubles will go away. You
shouldn't be running big software in the dom0 anyway. I always done that
because of habits from running older Xen (since 2.0.7), and because I've
seen issues with the dom0 ballooning out. To me, ballooning the memory
of dom0 is more a desktop feature than for a server.
I believe this bug should be closed, because that's not really an issue
with Xen (but more with the way the Linux dom0 kernel works). I'll let
Bastian decide though.
Thomas Goirand (zigo)
I agree that the dom0 shouldn't do heavy work and it doesn't. I will try your
suggestion; I had already looked for an option to set the max dom0 memory, but
couldn't find it (only a minimum one). I didn't think about kernel params.
I wonder though, if creating VM's when memory runs out even with a small dom0
will the still trigger the OOM killer. A nice warning about being out of memory
would be nicer...
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