astat.1

.TH "astat" "1" "2012" "astat" "Utils"
.SH "NAME"
astat \- Report CPU and IO statistics
.SH SYNOPSIS
.ft B
.B astat
.RB [ "\-d delay" ]
.RI [ blockdev " [ " blockdev " ]" ]
.SH DESCRIPTION
\fBastat\fP reports information about processes, CPU, memory, and block IO.

The report repeats every \fBdelay\fP seconds.  Block IO rates and memory sizes
are reported in MiB.  CPU usage is reported as percentages of a single core
across the entire SMP system, so for example on a four-core SMP the "user",
"nice", "system", "idle", "iowait", and "steal" columns will sum to 400. 

By default all block devices on the system are reported.  The user can specify a
smaller set on the command line if desired.  Either \fB/dev/sda\fP or \fBsda\fP
is supported.  The block device names must be the ones present in
\fB/sys/class/block\fP.  The device list can include partitions as well as
parent block devices.  Some small inaccuracies can be expected for partitions
due to IO coalescing done at the block device rather than the partition level;
see \fBlinux/Documentation/iostats.txt\fP for more details.

.SH OPTIONS
The \fB-d\fP
.I delay
option specifies the delay between updates in seconds.  If no delay is given,
a default of one second is used.  Only integer delays are supported.

.SH FIELD DESCRIPTIONS

.SS
.B "Processes and Interrupts"
.nf
ru: Number of processes running or waiting for runtime.
bl: Number of processes in uninterruptible sleep.
intr: Number of interrupts processed.
ctxsw: Number of context switches.
.fi
.PP
.SS
.B "CPU"
.nf
usr: Time spent running non\-kernel code.
nic: Time spent running niced processes.
sys: Time spent running kenerl code.
idl: Time spent idle.
iow: Time spent waiting for I/O to complete.
stl: Time stolen from a virtual machine.
.fi
.PP
.SS
.B "Memory"
All values are given in megabytes (MiB).
.nf
free: Free memory.
buff: Buffers.
cach: Cache memory.
actv: Active memory.
mlck: mlock(2)ed memory.
drty: Dirty memory.
wrbk: Memory waiting for writeback to block device.
.fi
.PP
.SS
.B "Block Devices"
.nf
dev: Block device name
rd: Number of read IO operations completed.
rMB: Size of reads completed.
wr: Number of write IO operations completed.
wMB: Size of writes completed.
io%: Percentage of time device was busy (had at least one IO request
outstanding).
avgms: Average IO completion time, in milliseconds.
depth: Instantaneous queue depth.
.fi

.SH "SEE ALSO"
.BR iostat (1),
.BR vmstat (8),
.BR sar (1),
.BR top (1)
.P
.SH BUGS
Symmetric Multithreading (SMT) and CPU clock scaling can affect the practical
accuracy of measuring "CPU utilization" based on scheduler timing.
.SH AUTHORS
Written by Andy Isaacson <adi@hexapodia.org>.