[Dnsmasq-discuss] dnsmasq running on RaspberryPi/ArchLinux slow to relay non-cached queries

Peter Bell peter at bellfamily.org.uk
Fri Aug 15 11:17:37 BST 2014


I have dnsmasq running on a RaspberryPi using the Arch Linux ARM 
distribution, implementing both dhcp and dns functionality (tftp is 
handled by a different server).

I have been experiencing extremely slow browsing performance - as an 
example, a 'first' google search takes, typically, 20 seconds to display 
the results page - the slowest I've recorded has been 30 seconds. 
Subsequent google searches complete within 2 seconds.

I have been complaining to my ISP for almost two months, blaming them 
for poor network performance, but they always reply that there are no 
issues on their network apart from some possible local contention 
issues.  However, even in the middle of the night, when speedtest is 
reporting 25Mbps down/15Mbps up, a google search can still take 20 
seconds or more.

The odd thing is that on a few occasions the network performance is 
perfect, when google results are always returned within 2 seconds - this 
happened last Tuesday, between the hours of 3am and 6pm.

Now I think that it might be 'egg-on-face' time because I'm beginning to 
think that my performance issues are being caused by my use of dnsmasq 
as my local dns server/relay.

My reasons for coming to this conclusion are based on some 
experimentation with dig.

If I dig an address directly at my ISP's dns server, it will, typically, 
report a query time of 500ms.  Repeating the query immediately will 
report a query time of around 50ms.

Performing the same, or similar, queries vis my dnsmasq server will 
often report a query time of 3 or four seconds, while an immediate 
repeat will report a query time of 0 or 1ms.  Similarly, queries for 
locally defined addresses, will report 0ms query times.

My conclusion from these tests is that dnsmasq takes an inordinately 
long time to return a query for an address that is neither in its cache, 
nor, possibly, in the ISP's dns server cache.

Unless this is a well-recognised phenomenon, I guess that I need to 
enable dns logging within dnsmasq and study the output - what should I 
expect to see in the log and what should I be looking for?

-- 
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Peter Bell                                Mob: +63 (0) 9287 340 343
Tagum City, Philippines.                  Tel: +63 (0) 84 216 9037
email/msn: peter at bellfamily.org.uk        Tel: +63 (0) 84 308 0002



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