Cpu load on small index small request per second

Hi

We use ES for our website with ~260 000 documents on 5 shards, which
represent approximately 915mo, on a 0.19.8 ES install.
We made request for fuzzy search with facet, and some facet filters with
filtered facets inside, the result was fast.
We get between ~30 request per seconds.
We begin with freebsd but get some high load like 7 on a 12 core server.
We try to change JVM to openjdk6-b25_1 and upgrade lucene to 3.6.1, but
with no success.
We add a debian server, we get between 1 and 1.5 load on the debian and 3
to 5 on the freebsd.
Both server have JVM memory configurate to 3go and never saturate, and we
have no cache eviction.
I add some bigdesk screenshot.

Is there minimal configuration parameters for production server we can have
miss ?

Thanks
Bastien Quelen

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