Forum: JRuby Jruby 1.6.7 & 1.7.0 high CPU usage with tomcat and rails 3.1.3 & 3.2.8

Trying to sort out high CPU usage with JRuby 1.6.7 running on tomcat 7,
rails 3.1.3.  A side note I have also tested with JRuby 1.7.0, tomcat 7 
and
rails 3.2.8 and have the same results but that and JAVA 7 are not in our
production environment yet, I'm trying to push it though.

We are running load tests and seeing the load on the box shoot up to 
100%
and response time be horrible after about 90 concurrent users to our
system.  I can't give many specifics but we are running with 8 runtimes. 
I
have tried running in threadsafe and it helps a little bit (we are 
having
some concurrency issues at high user load around 80 or so and database 
pool
issues around that same spot) but eventually the CPU spikes and never 
comes
down until we stop the load test.  Does anyone have some general "check
these things out" tips?  I'll try and provide extra information as 
needed
but the rails app is a heavy on the javascript with rails actions behind
the scenes to serve up data.  Which doesn't make sense as to why the 
server
load would shoot up for such a small number of users.  Lots of outgoing
http calls to a set of external API's as well.  I know, not a lot of 
info
but ask me whatever and I might be able to provide more.

Thanks