12.2 Overview of System
Performance
12.2 Overview of System
Performance
The following commands are the focus throughout this section.
The vmstat command syntax is as follows:
vmstat [ -f ] [ -i ] [ -s ] [ PhysicalVolume ... ] [ Interval [ Count ] ]
The vmstat command reports statistics about kernel threads, virtual memory, disks, traps, and CPU activity. Reports generated by the vmstat command can be used to balance system load activity. These system-wide statistics (among all processors) are calculated either as averages for values expressed as percentages or as sums.
The PhysicalVolume parameter can be used to specify one to four names. Transfer statistics are given for each specified drive in the order specified. This count represents requests to the physical device. It does not imply an amount of data that was read or written. Several logical requests can be combined into one physical request.
If the vmstat command is invoked without flags, the report contains a summary of the virtual memory activity since system startup. If the -f flag is specified, the vmstat command reports the number of forks since system startup. The PhysicalVolume parameter specifies the name of the physical volume.
The Interval parameter specifies the amount of time in seconds between each report. The first report contains statistics for the time since system startup. Subsequent reports contain statistics collected during the interval since the previous report. If the Interval parameter is not specified, the vmstat command generates a single report and then exits. The Count parameter can only be specified with the Interval parameter. If the Count parameter is specified, its value determines the number of reports generated and the number of seconds apart. If the Interval parameter is specified without the Count parameter, reports are continuously generated. A Count parameter of zero (0) is not allowed.
The kernel maintains statistics for kernel threads, paging, and interrupt activity, which the vmstat command accesses. The disk input/output statistics are maintained by device drivers. For disks, the average transfer rate is determined by using the active time and number of transfers information. The percent active time is computed from the amount of time the drive is busy during the report.
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Both the -f and -s flags can be entered on the command line, but the system will only accept the first flag specified and will override the second flag. |
Table 35 provides the key flags for the vmstat
command.
Table 35: Key Flags for the vmstat Command
The following are some examples using the vmstat command.
# vmstat kthr memory page faults cpu ----- ----------- ------------------------ ------------ ----------- r b avm fre re pi po fr sr cy in sy cs us sy id wa 0 0 19046 1554 0 0 0 0 0 0 117 310 30 0 1 99 1 #
# vmstat 2 5 kthr memory page faults cpu ----- ----------- ------------------------ ------------ ----------- r b avm fre re pi po fr sr cy in sy cs us sy id wa 0 0 19097 1498 0 0 0 0 0 0 117 310 30 0 1 99 1 0 0 19097 1498 0 0 0 0 0 0 121 168 34 0 1 99 0 0 0 19097 1498 0 0 0 0 0 0 126 118 34 0 0 99 0 0 0 19097 1498 0 0 0 0 0 0 121 118 38 0 0 99 0 0 0 19097 1498 0 0 0 0 0 0 122 121 34 0 0 99 0 #
The first summary (line one of the report) contains statistics for the time since boot.
# vmstat hdisk0 hdisk1 kthr memory page faults cpu disk xfer ----- ----------- ------------------------ ------------ ----------- ----------- r b avm fre re pi po fr sr cy in sy cs us sy id wa 1 2 3 4 0 0 18461 3284 0 0 0 0 0 0 117 310 30 0 1 99 1 0 0 #
# vmstat -f 13887 forks #
# vmstat -s
2205645 total address trans. faults
46745 page ins
135567 page outs
7088 paging space page ins
16737 paging space page outs
0 total reclaims
950333 zero filled pages faults
12659 executable filled pages faults
233034 pages examined by clock
15 revolutions of the clock hand
48272 pages freed by the clock
27557 backtracks
0 lock misses
10 free frame waits
0 extend XPT waits
38657 pending I/O waits
163907 start I/Os
163907 iodones
12734979 cpu context switches
49535570 device interrupts
0 software interrupts
0 traps
130379165 syscalls
#
Table 36 contains the column
headings and their description for vmstat output.
Table 36: vmstat Output Parameters
| Note |
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A large portion of real memory is utilized as a cache for file system data. It is not unusual for the size of the free list to remain small. |
The iostat command syntax is as follows:
iostat [ -d | -t ] [ PhysicalVolume ... ] [ Interval [ Count ] ]
The iostat command is used for monitoring system input/output device loading by observing the time the physical disks are active in relation to their average transfer rates. The iostat command generates reports that can be used to determine what changes should be made to the system configuration to better balance the input/output load between physical disks.
The first report generated by the iostat command provides statistics concerning the time since the system was booted.
Each subsequent report covers the time since the previous report. All statistics are reported each time the iostat command is run. The report consists of a TTY and CPU header row followed by a row of TTY and CPU statistics. On multiprocessor systems, CPU statistics are calculated system-wide as averages among all processors. A disks header row is displayed followed by a line of statistics for each disk that is configured. If the PhysicalVolume parameter is specified, only those names specified are displayed.
If the PhysicalVolume parameter is specified:
The first character in the PhysicalVolume parameter cannot be numeric.
The Interval parameter specifies the amount of time in seconds between each report. The first report contains statistics for the time since system startup (boot). Each subsequent report contains statistics collected during the interval since the previous report.
The Count parameter can be specified in conjunction with the Interval parameter. If the Count parameter is specified, the value of count determines the number of reports generated at Interval seconds apart. If the Interval parameter is specified without the Count parameter, the iostat command generates reports continuously.
The iostat command is useful in determining whether a physical volume is becoming a performance bottleneck and if there is potential to improve the situation. The % utilization field for the physical volumes indicates how evenly the file activity is spread across the drives. A high percentage utilization on a physical volume is a clear indication that there may be contention for this resource. Since the CPU utilization statistics are also available with the iostat report, the percentage of time the CPU is in I/O wait can be determined at the same time. Consider distributing data across drives if the I/O wait time is significant, and the disk utilization is not evenly distributed across volumes.
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Some system resource is consumed in maintaining disk I/O history for the iostat command. Use the sysconfig subroutine or SMIT to stop history accounting |
Table 37 provides a list of common iostat
command flags.
Table 37: Key Flags for the iostat Command
The following are examples of the iostat command usage.
#iostat
tty: tin tout avg-cpu: % user % sys % idle % iowait
0.1 32.9 5.9 17.0 32.3 44.8
Disks: % tm_act Kbps tps Kb_read Kb_wrtn
hdisk1 3.7 34.5 1.9 4664 128
hdisk0 46.5 526.3 40.2 68116 5048
cd0 0.0 0.0 0.0 0 0
#
iostat -d hdisk1 2
iostat -d hdisk1 2 6
iostat -d 2 6
iostat -d disk1 disk2 disk3 2 6
The iostat command generates two types of
reports, the tty and CPU Utilization report and the Disk Utilization report.
The meaning of the output parameters is shown in Table 38.
Table 38: iostat Output Parameters
For large system configurations where a large number of disks are configured, the system can be configured to avoid collecting physical disk input/output statistics when the iostat command is not executing. If the system is configured in the above manner, the first Disk report displays the message Disk History Since Boot Not Available instead of the disk statistics. Subsequent interval reports generated by the iostat command contain disk statistics collected during the report interval. Any TTY and CPU statistics after boot are unaffected. If a system management command is used to re-enable disk statistics, the first iostat command report displays activity from the interval starting at the point that disk input/output statistics were enabled.
The netstat command syntax is as follows:
To display active sockets for each protocol or routing table information:
/bin/netstat [ -n ] [ { -A -a } | { -r -i -I Interface } ] [ -f AddressFamily ] [ -p Protocol ] [ Interval ] [ System ]
To display the contents of a network data structure:
/bin/netstat [ -m | -s | -u | -v ] [ -f AddressFamily ] [ -p Protocol ] [ Interval ] [ System ]
To display the packet counts throughout the communications subsystem:
/bin/netstat -D
The netstat command (Table 39) symbolically
displays the contents of various network-related data structures for active
connections. The Interval parameter, specified in seconds, continuously
displays information regarding packet traffic on the configured network
interfaces. The Interval parameter takes no flags. The System parameter
specifies the memory used by the current kernel. Unless you are looking at a
dump file, the System parameter should be /unix.
Table 39: Key Flags for the netstat Command
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The following are examples of netstat command usage.
To display the routing table, use the command:
# netstat -r Routing tables Destination Gateway Flags Refs Use If PMTU Exp Groups Route Tree for Protocol Family 2 (Internet): default itsorusi.itsc.aus UG 14 706 tr0 - - 9.3/16 sv1051c.itsc.aust U 0 5 en0 - - 9.3.1/24 sv1051c.itsc.aust U 40 2616 tr0 - - 127/8 localhost U 3 180 lo0 - - 192.168.1/24 sv1166f.itsc.aust UG 0 0 tr0 - - Route Tree for Protocol Family 24 (Internet v6): ::1 ::1 UH 0 0 lo0 16896 - #
To display the routing statistics use the command:
# netstat -r -s
routing:
0 bad routing redirect
0 dynamically created route
0 new gateway due to redirects
0 destination found unreachable
0 use of a wildcard route
#
The default display for active sockets shows the following items:
Internet address formats are of the form host.port or network.port if a socket's address specifies a network but no specific host address. The host address is displayed symbolically if the address can be resolved to a symbolic host name while network addresses are displayed symbolically according to the /etc/networks file.
NS addresses are 12-byte quantities consisting of a 4-byte network number, a 6-byte host number, and a 2-byte port number, all of which are stored in network standard format. For VAX architecture, these are word and byte reversed; for the Sun systems, they are not reversed.
If a symbolic name for a host is not known, or if the -n flag is used, the address is printed numerically according to the address family. Unspecified addresses and ports appear as an * (asterisk).
Interface Display (netstat -i)
The interface display format provides a table of cumulative statistics for the following items:
The collision count for Ethernet interfaces is not supported.
The interface display also provides the:
Routing Table Display (netstat -r)
The routing table display format indicates the available routes and their statuses. Each route consists of a destination host or network and a gateway to use in forwarding packets. The routing table contains the following ten fields:
The flags field of the routing table shows the state of the route:
Direct routes are created for each interface attached to the local host.
12.4 Performance
Analysis