Hardware counter profiling records data when a SIGEMT signal (on Solaris platforms) or a SIGIO signal (on Linux platforms) is delivered to the target. It causes dilation to process that signal and unwind the call stack. Unlike clock profiling, for some hardware counters, different parts of the program might generate events more rapidly than other parts and show dilation in that part of the code. Any part of the program that generates such events very rapidly might be significantly distorted. Similarly, some events might be generated in one thread disproportionately to the other threads.