[jetty-user] why jetty7 is slower than jetty6?

I use jetty as a web server for solr, and I find a problem. solr replicate data from master to slave, and master uses a long http connection to write data 1M every time.I print the time cost every 1M transit, and find default's jetty7 cost is like 996ms,5ms,6ms,998ms,4ms,8ms,thus one time cost about 1s every 3 times. If I change to jetty6,it's so fast, and every time just cost less then 1ms.For jetty6 and jetty7,I just use default's conf, and the problem consist in both embed and external jetty . Who can tell me what I'm wrong?