iostats(4) [plan9 man page]

IOSTATS(4)						     Kernel Interfaces Manual							IOSTATS(4)

NAME

       iostats - file system to measure I/O

SYNOPSIS

       iostats cmd [ args...  ]

DESCRIPTION

       Iostats is a user-level file server that interposes itself between a program and the regular file server, which allows it to gather statis-
       tics 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.

       The report consists of three sections.  The first section reports the amount of user data in read and write messages sent  by  the  program
       and  the  average  rate	at which the data was transferred.  The protocol line reports the amount of data sent as message headers, that is,
       protocol overhead.  The rpc line reports the total number of file system transactions.

       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.

SOURCE

       /sys/src/cmd/iostats

BUGS

       Poor clock resolution means that large amounts of I/O must be done to get accurate rate figures.

       Can be fooled by programs that do fresh mounts outside its purview.

																	IOSTATS(4)

MNT(3)							     Library Functions Manual							    MNT(3)

NAME

       mnt - attach to 9P servers

SYNOPSIS

       #M

DESCRIPTION

       The  mount  driver  is used by the mount system call (but not bind; see bind(2)) to connect the name space of a process to the service pro-
       vided by a 9P server over a communications channel.  After the mount, system calls involving files in that portion of the name  space  will
       be converted by the mount driver into the appropriate 9P messages to the server.

       The  mount  system call issues session and attach(5) messages to the server to identify and validate the user of the connection.  Each dis-
       tinct user of a connection must mount it separately; the mount driver multiplexes the access of the various users and  their  processes	to
       the service.

       File-oriented system calls are converted by the kernel into messages in the 9P protocol.  Within the kernel, 9P is implemented by procedure
       calls to the various kernel device drivers.  The mount driver translates these procedure calls into remote procedure calls to be  transmit-
       ted as messages over the communication channel to the server.  Each message is implemented by a write of the corresponding protocol message
       to the server channel followed by a read on the server channel to get the reply.  Errors in the reply message are turned into  system  call
       error returns.

       A  read(2) or write system call on a file served by the mount driver may be translated into more than one message, since there is a maximum
       data size for a 9P message.  The system call will return when the specified number of bytes have been  transferred  or  a  short  reply	is
       returned.

       The string is an illegal file name, so this device can only be accessed directly by the kernel.

SEE ALSO

       bind(2)

SOURCE

       /sys/src/9/port/devmnt.c

BUGS

       When  mounting  a  service through the mount driver, that is, when the channel being multiplexed is itself a file being served by the mount
       driver, large messages may be broken in two.

																	    MNT(3)