nginx high memory usage in benchmarks

[Martin Reissner]

hello,
i've been running some benchmarks for static content with httperf and
autobench to compare nginx to apache's worker mpm. i used the default
config on apache (2 worker processes, 150 max clients) and set nginx to
use 2 worker processes with epoll and a keepalive_timeout of 15.
during the benchmarks i monitored the systems ressources with sar and
while i expected nginx to outperform apache in every way possible i
noticed that nginx uses way more ram than apache while staying ~1/3rd
behind it in cpu usage.

the benchmarks request a 10k file repeatedly over multiple persistent
connections and while apache used ~5mb throughout the tests nginx took
~70mb. can someone explain to me what the cause of this might be. from
what i read its low memory usage is one of the key features of nginx so
i'm pretty sure somethings wrong on my side.

martin