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SAR(1) Linux User's Manual SAR(1)
NAME
sar - Collect, report, or save system activity information.
SYNOPSIS
sar [ -A ] [ -b ] [ -B ] [ -c ] [ -C ] [ -d ] [ -i interval ] [ -p ] [ -q ] [ -r ] [ -R ]
[ -t ] [ -u ] [ -v ] [ -V ] [ -w ] [ -W ] [ -y ] [ -n { DEV | EDEV | NFS | NFSD | SOCK |
ALL } ] [ -I { irq | SUM | ALL | XALL } ] [ -P { cpu | ALL } ] [ -o [ filename ] | -f [
filename ] ] [ -s [ hh:mm:ss ] ] [ -e [ hh:mm:ss ] ] [ interval [ count ] ]
DESCRIPTION
The sar command writes to standard output the contents of selected cumulative activity
counters in the operating system. The accounting system, based on the values in the count
and interval parameters, writes information the specified number of times spaced at the
specified intervals in seconds. If the interval parameter is set to zero, the sar command
displays the average statistics for the time since the system was started. The default
value for the count parameter is 1. If its value is set to zero, then reports are gener-
ated continuously. The collected data can also be saved in the file specified by the -o
filename flag, in addition to being displayed onto the screen. If filename is omitted, sar
uses the standard system activity daily data file, the /var/log/sysstat/sadd file, where
the dd parameter indicates the current day. By default all the data available from the
kernel are saved in the data file.
The sar command extracts and writes to standard output records previously saved in a file.
This file can be either the one specified by the -f flag or, by default, the standard sys-
tem activity daily data file.
Without the -P flag, the sar command reports system-wide (global among all processors)
statistics, which are calculated as averages for values expressed as percentages, and as
sums otherwise. If the -P flag is given, the sar command reports activity which relates to
the specified processor or processors. If -P ALL is given, the sar command reports statis-
tics for each individual processor and global statistics among all processors.
You can select information about specific system activities using flags. Not specifying
any flags selects only CPU activity. Specifying the -A flag is equivalent to specifying
-bBcdqrRuvwWy -I SUM -I XALL -n ALL -P ALL.
The default version of the sar command (CPU utilization report) might be one of the first
facilities the user runs to begin system activity investigation, because it monitors major
system resources. If CPU utilization is near 100 percent (user + nice + system), the work-
load sampled is CPU-bound.
If multiple samples and multiple reports are desired, it is convenient to specify an out-
put file for the sar command. Run the sar command as a background process. The syntax for
this is:
sar -o datafile interval count >/dev/null 2>&1 &
All data is captured in binary form and saved to a file (datafile). The data can then be
selectively displayed with the sar command using the -f option. Set the interval and count
parameters to select count records at interval second intervals. If the count parameter is
not set, all the records saved in the file will be selected. Collection of data in this
manner is useful to characterize system usage over a period of time and determine peak
usage hours.
Note: The sar command only reports on local activities.
OPTIONS
-A This is equivalent to specifying -bBcdqrRuvwWy -I SUM -I XALL -n ALL -P ALL.
-b Report I/O and transfer rate statistics. The following values are displayed:
tps
Total number of transfers per second that were issued to physical devices.
A transfer is an I/O request to a physical device. Multiple logical requests
can be combined into a single I/O request to the device. A transfer is of
indeterminate size.
rtps
Total number of read requests per second issued to physical devices.
wtps
Total number of write requests per second issued to physical devices.
bread/s
Total amount of data read from the devices in blocks per second. Blocks are
equivalent to sectors with 2.4 kernels and newer and therefore have a size
of 512 bytes. With older kernels, a block is of indeterminate size.
bwrtn/s
Total amount of data written to devices in blocks per second.
-B Report paging statistics. Some of the metrics below are available only with post
2.5 kernels. The following values are displayed:
pgpgin/s
Total number of kilobytes the system paged in from disk per second. Note:
With old kernels (2.2.x) this value is a number of blocks per second (and
not kilobytes).
pgpgout/s
Total number of kilobytes the system paged out to disk per second. Note:
With old kernels (2.2.x) this value is a number of blocks per second (and
not kilobytes).
fault/s
Number of page faults (major + minor) made by the system per second. This
is not a count of page faults that generate I/O, because some page faults
can be resolved without I/O.
majflt/s
Number of major faults the system has made per second, those which have
required loading a memory page from disk.
pgfree/s
Number of pages placed on the free list by the system per second.
pgscank/s
Number of pages scanned by the kswapd daemon per second.
pgscand/s
Number of pages scanned directly per second.
pgsteal/s
Number of pages the system has reclaimed from cache (pagecache and swap-
cache) per second to satisfy its memory demands.
%vmeff
Calculated as pgsteal / pgscan, this is a metric of the efficiency of page
reclaim. If it is near 100% then almost every page coming off the tail of
the inactive list is being reaped. If it gets too low (e.g. less than 30%)
then the virtual memory is having some difficulty. This field is displayed
as zero if no pages have been scanned during the interval of time.
-c Report task creation activity.
proc/s
Total number of tasks created per second.
-C When reading data from a file, tell sar to display comments that have been inserted
by sadc.
-d Report activity for each block device (kernels 2.4 and newer only). When data is
displayed, the device specification dev m-n is generally used ( DEV column). m is
the major number of the device. With recent kernels (post 2.5), n is the minor
number of the device, but is only a sequence number with pre 2.5 kernels. Device
names may also be pretty-printed if option -p is used (see below). Values for
fields avgqu-sz, await, svctm and %util may be unavailable and displayed as 0.00
with some 2.4 kernels.
tps
Indicate the number of transfers per second that were issued to the device.
Multiple logical requests can be combined into a single I/O request to the
device. A transfer is of indeterminate size.
rd_sec/s
Number of sectors read from the device. The size of a sector is 512 bytes.
wr_sec/s
Number of sectors written to the device. The size of a sector is 512 bytes.
avgrq-sz
The average size (in sectors) of the requests that were issued to the
device.
avgqu-sz
The average queue length of the requests that were issued to the device.
await
The average time (in milliseconds) for I/O requests issued to the device to
be served. This includes the time spent by the requests in queue and the
time spent servicing them.
svctm
The average service time (in milliseconds) for I/O requests that were issued
to the device.
%util
Percentage of CPU time during which I/O requests were issued to the device
(bandwidth utilization for the device). Device saturation occurs when this
value is close to 100%.
-e [ hh:mm:ss ]
Set the ending time of the report. The default ending time is 18:00:00. Hours must
be given in 24-hour format. This option can be used when data are read from or
written to a file (options -f or -o ).
-f [ filename ]
Extract records from filename (created by the -o filename flag). The default value
of the filename parameter is the current daily data file, the /var/log/sysstat/sadd
file. The -f option is exclusive of the -o option.
-i interval
Select data records at seconds as close as possible to the number specified by the
interval parameter.
-I { irq | SUM | ALL | XALL }
Report statistics for a given interrupt. irq is the interrupt number. Specifying
multiple -I irq parameters on the command line will look at multiple independent
interrupts. The SUM keyword indicates that the total number of interrupts received
per second is to be displayed. The ALL keyword indicates that statistics from the
first 16 interrupts are to be reported, whereas the XALL keyword indicates that
statistics from all interrupts, including potential APIC interrupt sources, are to
be reported.
-n { DEV | EDEV | NFS | NFSD | SOCK | ALL }
Report network statistics.
With the DEV keyword, statistics from the network devices are reported. The fol-
lowing values are displayed:
IFACE
Name of the network interface for which statistics are reported.
rxpck/s
Total number of packets received per second.
txpck/s
Total number of packets transmitted per second.
rxkB/s
Total number of kilobytes received per second.
txkB/s
Total number of kilobytes transmitted per second.
rxcmp/s
Number of compressed packets received per second (for cslip etc.).
txcmp/s
Number of compressed packets transmitted per second.
rxmcst/s
Number of multicast packets received per second.
With the EDEV keyword, statistics on failures (errors) from the network devices are
reported. The following values are displayed:
IFACE
Name of the network interface for which statistics are reported.
rxerr/s
Total number of bad packets received per second.
txerr/s
Total number of errors that happened per second while transmitting packets.
coll/s
Number of collisions that happened per second while transmitting packets.
rxdrop/s
Number of received packets dropped per second because of a lack of space in
linux buffers.
txdrop/s
Number of transmitted packets dropped per second because of a lack of space
in linux buffers.
txcarr/s
Number of carrier-errors that happened per second while transmitting pack-
ets.
rxfram/s
Number of frame alignment errors that happened per second on received pack-
ets.
rxfifo/s
Number of FIFO overrun errors that happened per second on received packets.
txfifo/s
Number of FIFO overrun errors that happened per second on transmitted pack-
ets.
With the NFS keyword, statistics about NFS client activity are reported. The fol-
lowing values are displayed:
call/s
Number of RPC requests made per second.
retrans/s
Number of RPC requests per second, those which needed to be retransmitted
(for example because of a server timeout).
read/s
Number of 'read' RPC calls made per second.
write/s
Number of 'write' RPC calls made per second.
access/s
Number of 'access' RPC calls made per second.
getatt/s
Number of 'getattr' RPC calls made per second.
With the NFSD keyword, statistics about NFS server activity are reported. The fol-
lowing values are displayed:
scall/s
Number of RPC requests received per second.
badcall/s
Number of bad RPC requests received per second, those whose processing gen-
erated an error.
packet/s
Number of network packets received per second.
udp/s
Number of UDP packets received per second.
tcp/s
Number of TCP packets received per second.
hit/s
Number of reply cache hits per second.
miss/s
Number of reply cache misses per second.
sread/s
Number of 'read' RPC calls received per second.
swrite/s
Number of 'write' RPC calls received per second.
saccess/s
Number of 'access' RPC calls received per second.
sgetatt/s
Number of 'getattr' RPC calls received per second.
With the SOCK keyword, statistics on sockets in use are reported. The following
values are displayed:
totsck
Total number of sockets used by the system.
tcpsck
Number of TCP sockets currently in use.
udpsck
Number of UDP sockets currently in use.
rawsck
Number of RAW sockets currently in use.
ip-frag
Number of IP fragments currently in use.
tcp-tw
Number of TCP sockets in TIME_WAIT state.
The ALL keyword is equivalent to specifying all the keywords above and therefore
all the network activities are reported.
-o [ filename ]
Save the readings in the file in binary form. Each reading is in a separate record.
The default value of the filename parameter is the current daily data file, the
/var/log/sysstat/sadd file. The -o option is exclusive of the -f option.
-P { cpu | ALL }
Report per-processor statistics for the specified processor or processors. Speci-
fying the ALL keyword reports statistics for each individual processor, and glob-
ally for all processors. Of the flags which specify the statistics to be reported,
only the -u and -I SUM flags are meaningful with the -P flag. Note that processor 0
is the first processor.
-p Pretty-print device names. Use this option in conjunction with option -d. By
default names are printed as dev m-n where m and n are the major and minor numbers
for the device. Use of this option displays the names of the devices as they
(should) appear in /dev. Name mappings are controlled by /etc/sysstat/sys-
stat.ioconf.
-q Report queue length and load averages. The following values are displayed:
runq-sz
Run queue length (number of tasks waiting for run time).
plist-sz
Number of tasks in the task list.
ldavg-1
System load average for the last minute. The load average is calculated as
the average number of runnable or running tasks (R state), and the number of
tasks in uninterruptible sleep (D state) over the specified interval.
ldavg-5
System load average for the past 5 minutes.
ldavg-15
System load average for the past 15 minutes.
-r Report memory and swap space utilization statistics. The following values are dis-
played:
kbmemfree
Amount of free memory available in kilobytes.
kbmemused
Amount of used memory in kilobytes. This does not take into account memory
used by the kernel itself.
%memused
Percentage of used memory.
kbbuffers
Amount of memory used as buffers by the kernel in kilobytes.
kbcached
Amount of memory used to cache data by the kernel in kilobytes.
kbswpfree
Amount of free swap space in kilobytes.
kbswpused
Amount of used swap space in kilobytes.
%swpused
Percentage of used swap space.
kbswpcad
Amount of cached swap memory in kilobytes. This is memory that once was
swapped out, is swapped back in but still also is in the swap area (if mem-
ory is needed it doesn't need to be swapped out again because it is already
in the swap area. This saves I/O).
-R Report memory statistics. The following values are displayed:
frmpg/s
Number of memory pages freed by the system per second. A negative value
represents a number of pages allocated by the system. Note that a page has
a size of 4 kB or 8 kB according to the machine architecture.
bufpg/s
Number of additional memory pages used as buffers by the system per second.
A negative value means fewer pages used as buffers by the system.
campg/s
Number of additional memory pages cached by the system per second. A nega-
tive value means fewer pages in the cache.
-s [ hh:mm:ss ]
Set the starting time of the data, causing the sar command to extract records
time-tagged at, or following, the time specified. The default starting time is
08:00. Hours must be given in 24-hour format. This option can be used only when
data are read from a file (option -f ).
-t When reading data from a daily data file, indicate that sar should display the
timestamps in the original locale time of the data file creator. Without this
option, the sar command displays the timestamps in the user's locale time.
-u Report CPU utilization. The following values are displayed:
%user
Percentage of CPU utilization that occurred while executing at the user
level (application).
%nice
Percentage of CPU utilization that occurred while executing at the user
level with nice priority.
%system
Percentage of CPU utilization that occurred while executing at the system
level (kernel).
%iowait
Percentage of time that the CPU or CPUs were idle during which the system
had an outstanding disk I/O request.
%steal
Percentage of time spent in involuntary wait by the virtual CPU or CPUs
while the hypervisor was servicing another virtual processor.
%idle
Percentage of time that the CPU or CPUs were idle and the system did not
have an outstanding disk I/O request.
Note: On SMP machines a processor that does not have any activity at all (0.00 for
every field) is a disabled (offline) processor.
-v Report status of inode, file and other kernel tables. The following values are
displayed:
dentunusd
Number of unused cache entries in the directory cache.
file-nr
Number of file handles used by the system.
inode-nr
Number of inode handlers used by the system.
pty-nr
Number of pseudo-terminals used by the system.
-V Print version number then exit.
-w Report system switching activity.
cswch/s
Total number of context switches per second.
-W Report swapping statistics. The following values are displayed:
pswpin/s
Total number of swap pages the system brought in per second.
pswpout/s
Total number of swap pages the system brought out per second.
-y Report TTY device activity. The following values are displayed:
rcvin/s
Number of receive interrupts per second for current serial line. Serial line
number is given in the TTY column.
xmtin/s
Number of transmit interrupts per second for current serial line.
framerr/s
Number of frame errors per second for current serial line.
prtyerr/s
Number of parity errors per second for current serial line.
brk/s
Number of breaks per second for current serial line.
ovrun/s
Number of overrun errors per second for current serial line.
Note that with recent 2.6 kernels, these statistics can be retrieved only by root.
ENVIRONMENT
The sar command takes into account the following environment variables:
S_TIME_FORMAT
If this variable exists and its value is ISO then the current locale will be
ignored when printing the date in the report header. The sar command will use the
ISO 8601 format (YYYY-MM-DD) instead.
S_TIME_DEF_TIME
If this variable exists and its value is UTC then sar will save its data in UTC
time (data will still be displayed in local time). sar will also use UTC time
instead of local time to determine the current daily data file located in the
/var/log/sysstat directory. This variable may be useful for servers with users
located across several timezones.
EXAMPLES
sar -u 2 5
Report CPU utilization for each 2 seconds. 5 lines are displayed.
sar -I 14 -o int14.file 2 10
Report statistics on IRQ 14 for each 2 seconds. 10 lines are displayed. Data are
stored in a file called int14.file.
sar -r -n DEV -f /var/log/sysstat/sa16
Display memory, swap space and network statistics saved in daily data file 'sa16'.
sar -A
Display all the statistics saved in current daily data file.
BUGS
/proc filesystem must be mounted for the sar command to work.
All the statistics are not necessarily available, depending on the kernel version used.
FILES
/var/log/sysstat/sadd
Indicate the daily data file, where the dd parameter is a number representing the
day of the month.
/proc contains various files with system statistics.
AUTHOR
Sebastien Godard (sysstat <at> orange.fr)
SEE ALSO
sadc(8), sa1(8), sa2(8), sadf(1), isag(1), pidstat(1), mpstat(1), iostat(1), vmstat(8)
http://pagesperso-orange.fr/sebastien.godard/
Linux OCTOBER 2007 SAR(1)
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