Monthly Archives: December 2014

dns requests statistics

Posted by on December 20, 2014 No comments

Today I made huge investigation, why our DNS servers serve huge ammount of traffic 5Mb\s per server. (we have only 200000000 advertising requests).
Googling gives me ultimate utility!

dnstop

In ubuntu just

aptitude update; aptitude install dnstop

dnstop works via libpcap, so no matter what DNS Server you use. (bind, dnsmasq or powerdns).
I found, that some our mail relays were misconfigured and use master DNS servers instead of local bind cachers\resolvers. And solve huge DNS traffic issue.

So one more useful utility in addition to top,htop,iftop,mytop.
🙂

Is heaper threading enabled linux?

Posted by on December 5, 2014 No comments

How to check is heaper threading enabled at your server.

use /proc/cpuinfo
Some OPS recommend to check HT cpu flag, but according to manuals HT – for some processors mean HyperTransport for others mean Heaper Threading

Better way to count siblings

The kernel data Linux exposes in /proc/cpuinfo will show each logical cpu with a unique processor number. A logical cpu can be a hyperthreading sibling, a shared core in a dual or quad core, or a separate physical cpu. We must look at the siblings, cpu cores and core id to tell the difference.

If the number of cores = the number of siblings for a given physical processor, then hyperthreading is OFF.

cat /proc/cpuinfo | grep siblings | wc -l; cat /proc/cpuinfo | grep cores | wc -l