Caching DNS server (bind9.4.2) CPU usage is so so so high.

[Trần Trọng Tấn]

Hi, I have a caching-only dns server which get ~3k queries per second. Here
is specs:

Xeon dual-core 2,8GHz 4GB of RAM
Centos 5x 32bit (kernel 2.6.18-164.15.1.el5PAE)
bind 9.4.2

rndc status: recursive clients: 666/4900/5000

Bind always uses 100% on one core on single-thread config. After I
recompiled it to multi-thread, it uses nearly 200% on two core :( No iowait,
only sys and user. I searched around but didn't see any info about how bind
use CPU. Why does it become bottleneck?

One more thing, here is RAM usage:

cat /proc/meminfo
MemTotal:      4147876 kB
MemFree:       1863972 kB
Buffers:        143632 kB
Cached:         372792 kB
SwapCached:          0 kB
Active:        1916804 kB
Inactive:       276056 kB

 Do you have any idea?

TIA,

-giobuon
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