path: bpfcc_0.35.0+ds-1.1/tools/funcinterval.py
    ./funcinterval t:vmscan:mm_vmscan_direct_reclaim_begin
    # time the interval of c:malloc used by top every 3 seconds
    ./funcinterval -p `pidof -s top` -i 3 c:malloc
    # time /usr/local/bin/python main function
    ./funcinterval /usr/local/bin/python:main