a program has many threads,but only 4~5 threads running at a time,so does it hurt performace?

[pango]

my program create 400~500 threads at startup,but only 4~5 threads running at a time,other threads is blocked by calling WaitForSingleObject(),so does such a program hurt the performance of system?

[TimP]

Unless you are asking how Vtune might be used to check the performance, you might be interested in the Threading Forum and discussion of I/O Completion Ports.