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

NAME

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

SYNOPSIS

9       vfscount.bt
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 bpftrace.
23

EXAMPLES

25       Count all VFS calls until Ctrl-C is hit:
26              # vfscount.bt
27

FIELDS

29       1st    Kernel function name (in @[])
30
31       2nd    Number of calls while tracing
32

OVERHEAD

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

SOURCE

43       This is from bpftrace.
44
45              https://github.com/iovisor/bpftrace
46
47       Also look in the bpftrace distribution for  a  companion  _examples.txt
48       file containing example usage, output, and commentary for this tool.
49
50       This  is  a  bpftrace version of the bcc tool of the same name. The bcc
51       tool may provide more options and customizations.
52
53              https://github.com/iovisor/bcc
54

OS

56       Linux
57

STABILITY

59       Unstable - in development.
60

AUTHOR

62       Brendan Gregg
63

SEE ALSO

65       vfsstat.bt(8)
66
67
68
69USER COMMANDS                     2018-09-06                       vfscount(8)
Impressum