一，工具简介
funcslower主要可以显示内核或用户函数调用慢于既定阈值的情况。当基于聚合的工具失败时，它可以用于最后的诊断。
二，代码示例
#!/usr/bin/env python
from __future__ import print_function
from bcc import BPF
import argparse
import time
examples = """examples:
./funcslower vfs_write # trace vfs_write calls slower than 1ms
./funcslower -m 10 vfs_write # same, but slower than 10ms
./funcslower -u 10 c:open # trace open calls slower than 10us
./funcslower -p 135 c:open # trace pid 135 only
./funcslower c:malloc c:free # trace both malloc and free slower than 1ms
./funcslower -a 2 c:open # show first two arguments to open
./funcslower -UK -m 10 c:open # Show user and kernel stack frame of open calls slower than 10ms
./funcslower -f -UK c:open # Output in folded format for flame graphs
"""
parser = argparse.ArgumentParser(
description="Trace slow kernel or user function calls.",
formatter_class