perf usage

perf top 

perf top -p pid -G 

press ? would get the help menu, as the follow

shift + e would get the call chains 

perf record/report 

sudo perf record -p pid -g 

the data will written into file perf.data . we can specify another file with option -o 

sudo perf report -g or sudo perf report -g -i perf.data 

shift + e would get the callchains also 

sudo perf report -g --stdio