[Pdns-users] pdns-recursor: Only two threads used when threads=4

Grace Wang xiaohong.grace.wang at gmail.com
Thu Oct 20 22:53:11 UTC 2016

Sorry for not including a subject in the original post.

On Thu, Oct 20, 2016 at 3:51 PM, Grace Wang <xiaohong.grace.wang at gmail.com>

> Hi There,
> I installed pdns-recursor 4.0.3 on a CentOS 6.5 box, that has 20 physical
> cores and 128G RAM. When I set the threads in /etc/pdns-recursor/
> recursor.conf to be 4 or 12, then issued tons of queries (one query sent
> multiple times using multiple dnsperf instances simultaneously) at it, I
> noticed only 2 of the threads were working actively, each using almost 100%
> CPU and ~90% CPU, respectively. The other threads were using 0% CPU.
> With a previous version pdns-recursor 3.6.0 and the same test case, I
> could get 1 million qps, but with this new version that's supposed to have
> better performance, I am only getting ~200k qps.
> The way I installed it was by executing the following command (copied from
> the powerdns website):
> yum install epel-release yum-plugin-priorities && curl -o
> /etc/yum.repos.d/powerdns-rec-40.repo https://repo.powerdns.com/repo
> -files/centos-rec-40.repo && yum install pdns-recursor
> The only thing I changed was local-address, allow-from, and threads (in
> the /etc/pdns-recursor/recursor.conf file).
> Could you give me some insights on why this is happening, and what I
> should change in order to get all the threads to work?
> Thanks a lot,
> Grace
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