[Dnsmasq-discuss] CPU at 100%
Christopher Moore ( Linux Epos)
chris at linuxepos.com
Wed Jan 18 14:12:37 GMT 2012
-----Original message-----
To: Christopher Moore ( Linux Epos) <chris at linuxepos.com>;
CC: dnsmasq-discuss at lists.thekelleys.org.uk;
From: Simon Kelley <simon at thekelleys.org.uk>
Sent: Wed 18-01-2012 14:00
Subject: Re: [Dnsmasq-discuss] CPU at 100%
> On 18/01/12 13:35, Christopher Moore ( Linux Epos) wrote:
>
> >
> > Thanks for the quick reply.
> >
> > Dnsmasq is being started via:
> >
> > nice -n 0 initlog -q -c /usr/local/sbin/dnsmasq --cache-size=500
> --dns-forward-max=150
> >
> > Here's the output of lsof -c dnsmasq (This output was taken when the process
> is using 100% of the CPU) :
> >
> > COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
> > dnsmasq 16818 nobody cwd DIR 9,5 4096 2 /
> > dnsmasq 16818 nobody rtd DIR 9,5 4096 2 /
> > dnsmasq 16818 nobody txt REG 9,5 164296 22152
> /usr/local/sbin/dnsmasq
> > dnsmasq 16818 nobody mem REG 9,5 42496 775855
> /lib/libnss_files-2.10.1.so
> > dnsmasq 16818 nobody mem REG 9,5 1327456 775734
> /lib/libc-2.10.1.so
> > dnsmasq 16818 nobody mem REG 9,5 117348 355541
> /lib/ld-2.10.1.so
> > dnsmasq 16818 nobody 0u CHR 1,3 0t0 19603 /dev/null
> > dnsmasq 16818 nobody 1u CHR 1,3 0t0 19603 /dev/null
> > dnsmasq 16818 nobody 2u CHR 1,3 0t0 19603 /dev/null
> > dnsmasq 16818 nobody 3u IPv4 20851151 0t0 UDP *:domain
> > dnsmasq 16818 nobody 4u IPv4 20851152 0t0 TCP *:domain
> (LISTEN)
> > dnsmasq 16818 nobody 5r FIFO 0,6 0t0 20851159 pipe
> > dnsmasq 16818 nobody 6w FIFO 0,6 0t0 20851159 pipe
> > dnsmasq 16818 nobody 7u unix 0xf6ed9a80 0t0 20851162 socket
> >
> >
> > Dnsmasq configuration is :
> >
> > domain-needed
> > bogus-priv
> > resolv-file=/var/igaware/local/nameservers
> > user=nobody
> > group=nobody
> > interface=eth0
> > interface=eth1
> > interface=eth2
> > no-dhcp-interface=eth0
> > no-dhcp-interface=eth1
> > no-dhcp-interface=eth2
> > cache-size=500
> > local-ttl=3600
> >
> >
> > I have just realised that the eth2 interface doesn't actually exist on the
> machine, would that cuse a problem?
> >
>
>
> Lack of eth2 won't cause a problem.
>
> If would be useful to see the output of lsof _before_ the 100% CPU
> phase. What's obvious from the information we already have is that:
>
> 1) The netlink socket which should be open, isn't.
>
> 2) dnsmasq believes that the netlink socket is open and that it's file
> descriptor zero.
>
> File descriptor zero is actually open to /dev/null (that's OK). My guess
> is that something, somewhere on the machine writing to /dev/null is
> enough to make it ready for reading in select() and that's when the 100%
> CPU thing starts.
>
> I assume because it's in /usr/local/sbin that this is a locally-compiled
> binary. It's not locally-modified code, is it?
>
>
> Cheers,
>
> Simon.
Hi,
Here's lsof when things are OK:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dnsmasq 12073 nobody cwd DIR 9,5 4096 2 /
dnsmasq 12073 nobody rtd DIR 9,5 4096 2 /
dnsmasq 12073 nobody txt REG 9,5 164296 22152 /usr/local/sbin/dnsmasq
dnsmasq 12073 nobody mem REG 9,5 42496 775855 /lib/libnss_files-2.10.1.so
dnsmasq 12073 nobody mem REG 9,5 1327456 775734 /lib/libc-2.10.1.so
dnsmasq 12073 nobody mem REG 9,5 117348 355541 /lib/ld-2.10.1.so
dnsmasq 12073 nobody 0u CHR 1,3 0t0 19603 /dev/null
dnsmasq 12073 nobody 1u CHR 1,3 0t0 19603 /dev/null
dnsmasq 12073 nobody 2u CHR 1,3 0t0 19603 /dev/null
dnsmasq 12073 nobody 3u netlink 0t0 20962043 ROUTE
dnsmasq 12073 nobody 4u IPv4 20962047 0t0 UDP *:domain
dnsmasq 12073 nobody 5u IPv4 20962048 0t0 TCP *:domain (LISTEN)
dnsmasq 12073 nobody 6r FIFO 0,6 0t0 20962055 pipe
dnsmasq 12073 nobody 7w FIFO 0,6 0t0 20962055 pipe
dnsmasq 12073 nobody 8u unix 0xe2ca4a40 0t0 20962058 socket
ls -l /dev/null
crwxrwxrwx 1 root root 1, 3 Jul 18 2001 /dev/null
The binary is locally compiled, but the source isn't modified.
Regards, Chris.
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