freebsd-dev/usr.sbin/pstat/pstat.8
Ed Schouten c0086bf202 Serialize write() calls on TTYs.
Just like the old TTY layer, the current MPSAFE TTY layer does not make
any attempt to serialize calls of write(). Data is copied into the
kernel in 256 (TTY_STACKBUF) byte chunks. If a write() call occurs at
the same time, the data may interleave. This is especially likely when
the TTY starts blocking, because the output queue reaches the high
watermark.

I've implemented this by adding a new flag, TTY_BUSY_OUT, which is used
to mark a TTY as having a thread stuck in write(). Because I don't want
non-blocking processes to be possibly blocked by a sleeping thread, I'm
still allowing it to bypass the protection. According to this message,
the Linux kernel returns EAGAIN in such cases, but I think that's a
little too restrictive:

	http://kerneltrap.org/index.php?q=mailarchive/linux-kernel/2007/5/2/85418/thread

PR:		kern/118287
2009-02-11 16:28:49 +00:00

252 lines
6.4 KiB
Groff

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.\" @(#)pstat.8 8.5 (Berkeley) 5/13/94
.\" $FreeBSD$
.\"
.Dd August 20, 2008
.Dt PSTAT 8
.Os
.Sh NAME
.Nm pstat ,
.Nm swapinfo
.Nd display system data structures
.Sh SYNOPSIS
.Nm
.Op Fl Tfghkmnst
.Op Fl M Ar core Op Fl N Ar system
.Nm swapinfo
.Op Fl ghkm
.Op Fl M Ar core Op Fl N Ar system
.Sh DESCRIPTION
The
.Nm
utility displays open file entry, swap space utilization,
terminal state, and vnode data structures.
.Pp
If invoked as
.Nm swapinfo
the
.Fl s
option is implied, and only the
.Fl k , m , g ,
and
.Fl h
options are legal.
.Pp
If the
.Fl M
option is not specified, information is obtained from
the currently running kernel via the
.Xr sysctl 3
interface.
Otherwise, information is read from the specified core file,
using the name list from the specified kernel image (or from
the default image).
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl n
Print devices out by major/minor instead of name.
.It Fl h
.Dq Human-readable
output.
Use unit suffixes when printing swap partition sizes:
Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte.
.It Fl k
Print sizes in kilobytes, regardless of the setting of the
.Ev BLOCKSIZE
environment variable.
.It Fl m
Print sizes in megabytes, regardless of the setting of the
.Ev BLOCKSIZE
environment variable.
.It Fl g
Print sizes in gigabytes, regardless of the setting of the
.Ev BLOCKSIZE
environment variable.
.It Fl T
Print the number of used and free slots in several system tables.
This is useful for checking to see how large system tables have become
if the system is under heavy load.
.It Fl f
Print the open file table with these headings:
.Bl -tag -width indent
.It LOC
The core location of this table entry.
.It TYPE
The type of object the file table entry points to.
.It FLG
Miscellaneous state variables encoded thus:
.Pp
.Bl -tag -width indent -compact
.It R
open for reading
.It W
open for writing
.It A
open for appending
.It I
signal pgrp when data ready
.El
.It CNT
Number of processes that know this open file.
.It MSG
Number of messages outstanding for this file.
.It DATA
The location of the vnode table entry or socket structure for this file.
.It OFFSET
The file offset (see
.Xr lseek 2 ) .
.El
.It Fl s
Print information about swap space usage on all the
swap areas compiled into the kernel.
The first column is the device name of the partition.
The next column is
the total space available in the partition.
The
.Ar Used
column indicates the total blocks used so far; the
.Ar Available
column indicates how much space is remaining on each partition.
The
.Ar Capacity
reports the percentage of space used.
.Pp
If more than one partition is configured into the system, totals for all
of the statistics will be reported in the final line of the report.
.It Fl t
Print table for terminals
with these headings:
.Bl -tag -width indent
.It LINE
Device name.
.It INQ
Number of characters that can be stored in the input queue.
.It CAN
Number of characters in the input queue which can be read.
.It LIN
Number of characters in the input queue which cannot be read yet.
.It LOW
Low water mark for input.
.It OUTQ
Number of characters that can be stored in the output queue.
.It USE
Number of bytes in the output queue.
.It LOW
Low water mark for output.
.It COL
Calculated column position of terminal.
.It SESS
Kernel address of the session structure.
.It PGID
Process group for which this is the controlling terminal.
.It STATE
Miscellaneous state variables encoded thus:
.Pp
.Bl -tag -width indent -compact
.It I
init/lock-state device nodes present
.It C
callout device nodes present
.It O
opened
.It c
console in use
.It G
gone
.It B
busy in
.Xr open 2
.It Y
send SIGIO for input events
.It L
next character is literal
.It H
high watermark reached
.It X
open for exclusive use
.It S
output stopped (ixon flow control)
.It l
block mode input routine in use
.It Z
connection lost
.It s
i/o being snooped
.It b
busy in
.Xr read 2
or
.Xr write 2
.El
.Pp
The
.Ql i
and
.Ql o
characters refer to the previous character, to differentiate between
input and output.
.El
.It Fl M
Extract values associated with the name list from the specified core.
.It Fl N
If
.Fl M
is also specified,
extract the name list from the specified system instead of the default,
which is the kernel image the system has booted from.
.El
.Sh SEE ALSO
.Xr ps 1 ,
.Xr systat 1 ,
.Xr stat 2 ,
.Xr fs 5 ,
.Xr iostat 8 ,
.Xr vmstat 8
.Rs
.%T UNIX Implementation
.%A K. Thompson
.Re
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.0 .
.Sh BUGS
Does not understand
.Tn NFS
swap servers.