profiling functions called in interrupt context

Hi , i want to measure time spend in a callback function called from interrupt context . since the time spend will be in us / ns , what kernel apis can i use to measure it ? also since i want to use it in interrupt context , kernel time measurement apis should not sleep . i am using embedded arm target , and tools like OProfile are not available . can i be guided which kernel time measurement apis shall i use to measure time in a interrupt callback ? Regards Amit Nagal