Suprisingly expensive volatiles

The java keyword volatile defines a variable to always be written to main memory before some other method access it. It's important to notice that this write to main memory takes about 1000 clockcycles on a modern CPU, since the variable has to traverse three layers of cache to get there. The use of volatile should be very carefully investigated. The blog Mechanical Sympathy wrote more about the use of volatile variables two and a half year ago.