`java.net.Socket::setPerformancePreferences` was introduced in Java 1.5 with the intention of providing a declarative API for configuring the performance-wise characteristics of the underlying socket. It has always been a no-op and a corpus search does not reveal any significant usages of it. JDK-8366575 proposes removing the SDP support, and this further undermines the value of `setPerformancePreferences`. This issue proposes deprecating the method.