[Dnsmasq-discuss] dnsmasq process in S, D state causing high load average

[Simon Kelley]

Best I can suggest is to fix the cause of some interfaces failing the
DAD test. Failing that, patch dnsmasq to avoid the polling looking for
DAD to succeed.

Cheers,

Simon



On 17/02/16 12:53, green krypton wrote:
> 500 instances in 500 vlans
> 
> On Sat, Nov 21, 2015 at 3:05 AM, Simon Kelley <simon at thekelleys.org.uk>
> wrote:
> 
>> On 18/11/15 12:23, green krypton wrote:
>>> I have around 500 dnsmasq process which are configured to give ipv6,ipv4
>>> addresses out of this some fluctuate between D and S state while others
>> are
>>> in continuous S state.Probably because of too many processes in D state
>>> with "rtnetlink_rcv" in wchan its showing very high load average.
>>>
>>>
>>> functions in stack when in D state:
>>>
>>> [<ffffffff816360a9>] rtnetlink_rcv+0x19/0x30
>>> [<ffffffff81653e25>] netlink_unicast+0xd5/0x1b0
>>> [<ffffffff8165420e>] netlink_sendmsg+0x30e/0x680
>>> [<ffffffff8160e32b>] sock_sendmsg+0x8b/0xc0
>>> [<ffffffff8160e871>] SYSC_sendto+0x121/0x1c0
>>> [<ffffffff8160f25e>] SyS_sendto+0xe/0x10
>>> [<ffffffff817342dd>] system_call_fastpath+0x1a/0x1f
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>>
>>> but in couple of seconds it changes to S state with this in stack,all
>> idle
>>> process have this in stack.
>>>
>>> [<ffffffff811d20d9>] poll_schedule_timeout+0x49/0x70
>>> [<ffffffff811d2ac6>] do_select+0x5b6/0x780
>>> [<ffffffff811d2e5c>] core_sys_select+0x1cc/0x2e0
>>> [<ffffffff811d301b>] SyS_select+0xab/0x100
>>> [<ffffffff817342dd>] system_call_fastpath+0x1a/0x1f
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>>
>>>
>>> interface in which dnsmasq is listening has " tentative dadfailed" in
>> "scope
>>> global" error for ipv6 .
>>>
>>> Not able to understand why dnsmasq that are connected to interfaces that
>>> have "tentative dadfailed " continuously changes between S and D state
>>> while others are idle.
>>>
>>> attached is the strace while dnsmasq is in D state.
>>>
>>> Any idea about this issue?
>>>
>>>
>>
>> Dnsmasq polls every second whilst one or more interfaces it's listening
>> on are still doing DAD. Once all interfaces have completed DAD,it stops
>> polling.
>>
>>
>> Are you really running 500 separate instances on dnsmasq? That's an
>> installation which is way out of the normal way of doing things.
>>
>>
>> Cheers,
>>
>> Simon.
>>
>>>
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>>
>>
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