bcc-vfscount(8)

1vfscount(8)                 System Manager's Manual                vfscount(8)
2
3
4

NAME

6       vfscount - Count VFS calls ("vfs_*"). Uses Linux eBPF/bcc.
7

SYNOPSIS

9       vfscount
10

DESCRIPTION

12       This  counts VFS calls. This can be useful for general workload charac‐
13       terization of these operations.
14
15       This works by tracing all kernel functions beginning with "vfs_"  using
16       dynamic  tracing. This may match more functions than you are interested
17       in measuring: Edit the script to customize which functions to trace.
18
19       Since this uses BPF, only the root user can use this tool.
20

REQUIREMENTS

22       CONFIG_BPF and bcc.
23

EXAMPLES

25       Count some VFS calls until Ctrl-C is hit:
26              # vfscount
27
28       Count some VFS calls in ten seconds
29              # vfscount 10
30

FIELDS

32       ADDR   Address of the instruction pointer that was traced (only  useful
33              if  the  FUNC  column is suspicious and you would like to double
34              check the translation).
35
36       FUNC   Kernel function name
37
38       COUNT  Number of calls while tracing
39

OVERHEAD

41       This traces kernel vfs functions and maintains in-kernel counts,  which
42       are  asynchronously  copied to user-space. While the rate of VFS opera‐
43       tions can be very high (>1M/sec), this is a relatively efficient way to
44       trace  these  events,  and  so the overhead is expected to be small for
45       normal workloads.  Measure in a test environment, and if overheads  are
46       an  issue,  edit the script to reduce the types of vfs functions traced
47       (currently all beginning with "vfs_").
48

SOURCE

50       This is from bcc.
51
52              https://github.com/iovisor/bcc
53
54       Also look in the bcc distribution for a  companion  _examples.txt  file
55       containing example usage, output, and commentary for this tool.
56

OS

58       Linux
59

STABILITY

61       Unstable - in development.
62

AUTHOR

64       Brendan Gregg
65