Hi, I have a Solr+Tomcat installation on an 8 CPU Linux box, and I just tried sending parallel requests to it and measuring response time. I would expect that it could handle up to 8 parallel requests without significant slowdown of any individual request.
Instead, I found that Tomcat is serializing the requests. For example, the response time for each of 2 parallel requests is nearly 2 times that for a single request, and the time for each of 8 parallel requests is about 4 times that of a single request. I am pretty sure this is a Tomcat issue, for when I started 8 identical instances of Solr+Tomcat on the machine (on 8 different ports), I could send one request to each in parallel with only a 20% slowdown (compared to 300% in a single Tomcat.) I'm using the stock Tomcat download with minimal configuration changes, except that I disabled all logging (in case the logger was blocking for each request, serializing them.) I'm giving 2G RAM to each JVM. Does anyone more familiar with Tomcat know what's wrong? I can't imagine that Tomcat really can't handle parallel requests.
