FS_USAGE(1) BSD General Commands Manual FS_USAGE(1)
NAME
fs_usage -- report system calls and page faults related to filesystem activity in real-time
SYNOPSIS
fs_usage [-e] [-w] [-f mode [-f mode] ...] [pid|cmd [pid|cmd] ...]
DESCRIPTION
The fs_usage utility presents an ongoing display of system call usage information pertaining to
filesystem activity. It requires root privileges due to the kernel tracing facility it uses to oper-ate. operate.
ate. By default the activity monitored includes all system processes except the running fs_usage
process, Terminal, telnetd, sshd, rlogind, tcsh, csh and sh. These defaults can be overridden such
that output is limited to include or exclude a list of processes specified by the user.
The output presented by fs_usage is formatted according to the size of your window. A narrow window
will display fewer columns of data. Use a wide window for maximum data display. You may override the
window formatting restrictions by forcing a wide display with the -w option. In this case, the data
displayed will wrap when the window is not wide enough.
The options are as follows:
-e Specifying the -e option generates output that excludes sampling of the running fs_usage tool.
If a list of process ids or commands is also given, then those processes are also excluded from
the sampled output.
-f Specifying the -f option turns on output filtering based on the mode provided. Multiple fil-tering filtering
tering options can be specified. By default no output filtering occurs. The supported modes
are:
network Only network related output is displayed.
filesys Only file system related output is displayed.
cachehit In addition, display CACHE_HIT output.
-w Specifying the -w option forces a wider, more detailed output, regardless of the window size.
pid | cmd
The sampled data can be limited to a list of process ids or commands. When a command name is
given, all processes with that name will be sampled. Using the -e option has the opposite
effect, excluding sampled data relating to the given list of process ids or commands.
If you set the DYLD_IMAGE_SUFFIX environment variable to ``_debug'', then an application will use the
debug version of all libraries, including the Carbon FileManager. See dyld(1). When fs_usage is run
against a Carbon Application launched in this environment, then the high-level Carbon FileManager calls
will be displayed bracketing the system calls that they are built on.
The data columns displayed are as follows:
TIMESTAMP
TOD when call occurred. Wide mode will have millisecond granularity.
CALL The name of the network or filesystem related call, page-in, page-out, or physical disk access.
FILE DESCRIPTOR
Of the form F=x, x is a file descriptor. Depending on the type of system call, this will be
either an input value or a return value.
BYTE COUNT
Of the form B=x, x is the number of bytes requested by the call.
[ERRNO]
On error, the errno is displayed in brackets.
PATHNAME
Pathname of the file accessed (up to the last 28 bytes).
FAULT ADDRESS
Of the form A=0xnnnnnnnn, where 0xnnnnnnnn is the address being faulted.
DISK BLOCK NUMBER
Of the form D=0xnnnnnnnn, where 0xnnnnnnnn is the block number of the physical disk block being
read or written.
OFFSET Of the form O=0xnnnnnnnn, where 0xnnnnnnnn is a file offset.
SELECT RETURN
Of the form S=x, x is the number of ready descriptors returned by the select() system call. If
S=0, the time limit expired.
TIME INTERVAL(W)
The elapsed time spent in the system call. A `W' after the elapsed time indicates the process
was scheduled out during this file activity. In this case, the elapsed time includes the wait
time.
PROCESS NAME
The process that made the system call.
SAMPLE USAGE
fs_usage -w -f filesys Mail
fs_usage will display file system related data for all instances of processes named Mail. Maximum data
output will be displayed in the window.
SEE ALSO
dyld(1), latency(1), sc_usage(1), top(1)
Mac OS X November 7, 2002 Mac OS X
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