Caching DNS server (bind9.2) CPU usage is so so so high
- by Gk.
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 (kernel 2.6.18-164.15.1.el5PAE)
bind 9.4.2
rndc status:
recursive clients: 666/4900/5000
About 300 new queries (not in cache) per second.
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
I've set max-cache-size to 0 to make sure bind can use as much RAM as it want, but it always stop at ~2GB. Since every second we got not cached queries so theoretically RAM must be exhausted but it wasn't.
Do you have any idea?
TIA,
-Gk
