The initial report is from here:
http://mail.openjdk.java.net/pipermail/jdk8-dev/2013-October/003380.html

This regression manifests either with direct invoker call, or the invoker bootstrapped into the constant call site first.

JDK 7u15:
50.909 +- 0.407 ops/us, o.o.p.ConstantCallSiteBench.baseline
50.217 +- 0.216 ops/us, o.o.p.ConstantCallSiteBench.testInvoker
50.764 +- 0.836 ops/us, o.o.p.DirectBench.baseline
29.211 +- 0.208 ops/us, o.o.p.DirectBench.testInvoker

JDK 7u40:
57.386 +- 0.267 ops/us, o.o.p.ConstantCallSiteBench.baseline
  4.559 +- 0.082 ops/us, o.o.p.ConstantCallSiteBench.testInvoker
54.099 +- 3.921 ops/us, o.o.p.DirectBench.baseline
  4.197 +- 0.094 ops/us, o.o.p.DirectBench.testInvoker

The benchmarks are available here (*.zip requires JMH to build, *.jar is executable JAR)
 http://cr.openjdk.java.net/~shade/8026288/