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- .TH IOSTATS 4
- .SH NAME
- iostats \- file system to measure I/O
- .SH SYNOPSIS
- .B iostats
- [
- .B -d
- ]
- [
- .B -f
- .I dbfile
- ]
- .I cmd
- [
- .I args...
- ]
- .SH DESCRIPTION
- .I Iostats
- is a user-level file server that interposes itself between a program
- and the regular file server, which
- allows it to gather statistics of file system
- use at the level of the Plan 9 file system protocol, 9P.
- After a program
- exits a report is printed on standard error.
- .PP
- The report consists of three sections.
- The first section reports the amount
- of user data in
- .B read
- and
- .B write
- messages sent by the program and the average rate at
- which the data was transferred.
- The
- .B protocol
- line reports the amount
- of data sent as message headers, that is,
- protocol overhead.
- The
- .B rpc
- line reports the
- total number of file system transactions.
- .PP
- The second section gives
- the number of messages, the fastest, slowest, and average turn around
- time and the amount of data involved with each 9P
- message type.
- The final section gives an I/O summary for each file used
- by the program in terms of opens, reads and writes.
- .PP
- If the
- .B -d
- flag is present, a debugging log including all traffic
- is written to
- .I dbfile
- (default
- .BR iostats.out ).
- .SH EXAMPLE
- Display summary of file I/O incurred by
- .IR ls (1):
- .IP
- .EX
- iostats ls
- .EE
- .PP
- Start a new shell, displaying all 9P traffic caused by the shell or its children:
- .IP
- .EX
- iostats -df /fd/1 rc
- .EE
- .SH SOURCE
- .B /sys/src/cmd/iostats
- .SH BUGS
- Poor clock resolution means that large amounts of I/O must be done to
- get accurate rate figures.
- .PP
- Can be fooled by programs that do fresh mounts outside its purview.
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