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Re: [Xen-users] XM sched-credit

To: Florian Heigl <florian.heigl@xxxxxxxxx>
Subject: Re: [Xen-users] XM sched-credit
From: Paul Piscuc <paul.piscuc@xxxxxxxxxx>
Date: Wed, 19 Jan 2011 14:23:10 +0200
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Yes, this might be a solution. The problem is that on the Dom0 I have no application running, except for the firewall, and some nagios plugins, that are interrogated by the nagios server. When one guest requires a lot of CPU, the nagios server sends an alert that the Dom0 is not responding, although is has no load or other issues. This happens almost once a week, and the guest OS is used for a database server.

What would be a better solution ... to pin a cpu for dom0, to change the weight for dom0, or to continue using the same sched-credit, and tune the nagios server to wait for Dom0 longer?

Thx in advance.
yes. seems you allocated all cpu ressources away from dom0.
can you try pinning the vm to one cpu and dom0 to another?


2011/1/14 Paul Piscuc<paul.piscuc@xxxxxxxxxx>:

I have modified the sched-credit for one virtual machine, using xm
sched-credit -d 0 -w 60000, and the next day Nagios reported some problems
on Dom0. Two plugins, that are checking the firewall and smartctl reported
"socket timeout after 10 seconds". When I issued the two scripts, one of
them took 5 seconds to run, and the other one a few minutes. Here is the
first command that took 5 seconds:

/sbin/iptables-save|grep -v '^\*' |grep -v '^#' |grep -v '^COMMIT'|grep -v
'^:'|wc -l

When straced, it pauses for a long time in wait4(). When issued several
times, it waits a long time on the third or forth grep. The second one does
the same in read(). The load on the dom0 is 0.02, ulimit is ok,and there is
no waiting time for the cpu. Also, the virtual machines are running
smoothly, without high IO, memory or CPU.

Could the problem be generated by the scheduler, that allocated a small
weight for the dom0?

Thx in advance,


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