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Test Your Knowledge in Computers #767
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A victim cache is a cache used to hold blocks evicted from a CPU cache upon replacement.
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vmstat(1) [bsd man page]

VMSTAT(1)						      General Commands Manual							 VMSTAT(1)

NAME
vmstat - report virtual memory statistics SYNOPSIS
vmstat [ -fsi ] [ drives ] [ interval [ count ] ] DESCRIPTION
Vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and cpu activity. If given a -f argument, it instead reports on the number of forks and vforks since system startup and the number of pages of virtual memory involved in each kind of fork. If given a -s argument, it instead prints the contents of the sum structure, giving the total number of several kinds of paging related events which have occurred since boot. If given a -i argument, it instead reports on the number of inter- rupts taken by each device since system startup. If none of these options are given, vmstat will report in the first line a summary of the virtual memory activity since the system has been booted. If interval is specified, then successive lines are summaries over the last interval seconds. ``vmstat 5'' will print what the system is doing every five seconds; this is a good choice of printing interval since this is how often some of the statistics are sampled in the system; others vary every second, running the output for a while will make it apparent which are recomputed every second. If a count is given, the statistics are repeated count times. The format fields are: Procs: information about numbers of processes in various states. r in run queue b blocked for resources (i/o, paging, etc.) w runnable or short sleeper (< 20 secs) but swapped Memory: information about the usage of virtual and real memory. Virtual pages are considered active if they belong to processes which are running or have run in the last 20 seconds. A ``page'' here is 1024 bytes. avm active virtual pages fre size of the free list Page: information about page faults and paging activity. These are averaged each five seconds, and given in units per second. re page reclaims (simulating reference bits) at pages attached (found in free list) pi pages paged in po pages paged out fr pages freed per second de anticipated short term memory shortfall sr pages scanned by clock algorithm, per-second up/hp/rk/ra: Disk operations per second (this field is system dependent). Typically paging will be split across several of the available drives. The number under each of these is the unit number. Faults: trap/interrupt rate averages per second over last 5 seconds. in (non clock) device interrupts per second sy system calls per second cs cpu context switch rate (switches/sec) Cpu: breakdown of percentage usage of CPU time us user time for normal and low priority processes sy system time id cpu idle If more than 4 disk drives are configured in the system, vmstat displays only the first 4 drives, with priority given to Massbus disk drives (i.e. if both Unibus and Massbus drives are present and the total number of drives exceeds 4, then some number of Unibus drives will not be displayed in favor of the Massbus drives). To force vmstat to display specific drives, their names may be supplied on the command line. FILES
/dev/kmem, /vmunix SEE ALSO
systat(1), iostat(1) The sections starting with ``Interpreting system activity'' in Installing and Operating 4.2bsd. 4th Berkeley Distribution March 15, 1986 VMSTAT(1)

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vmstat(1)						      General Commands Manual							 vmstat(1)

NAME
vmstat - report virtual memory statistics SYNOPSIS
[interval [count]] | | DESCRIPTION
The command reports certain statistics kept about process, virtual memory, trap, and CPU activity. It also can clear the accumulators in the kernel structure. Options recognizes the following options: Report disk transfer information as a separate section, in the form of transfers per second. Provide an output format that is more easily viewed on an 80-column display device. This format separates the default output into two groups: vir- tual memory information and CPU data. Each group is displayed as a separate line of output. On multiprocessor systems, this display format also provides CPU utilization on a per CPU basis for the active processors. Report the number of processes swapped in and out and instead of page reclaims and address translation faults and interval Display successive lines which are summaries over the last interval seconds. The first line reported is for the time since a reboot and each subsequent line is for the last interval only. If interval is zero, the output is displayed once only. If the option is specified, the column headers are repeated. If is omitted, the column headers are not repeated. The command prints what the system is doing every five seconds. This is a good choice of printing interval since this is how often some of the statistics are sampled in the system; others vary every second. count Repeat the summary statistics count times. If count is omitted or zero, the output is repeated until an interrupt or quit signal is received. From the terminal, these are commonly and respectively (see stty(1)). Report on the number of forks and the number of pages of virtual memory involved since boot-up. Print the total number of several kinds of paging-related events from the kernel structure that have occurred since boot-up or since was last executed with the option. Clear all accumulators in the kernel structure. This option is restricted to the super user. If none of these options is given, displays a one-line summary of the virtual memory activity since boot-up or since the option was last executed. Column Descriptions The column headings and the meaning of each column are: Information about numbers of processes in various states. In run queue Blocked for resources (I/O, paging, etc.) Runnable or short sleeper (< 20 secs) but swapped Information about the usage of virtual and real memory. Virtual pages are considered active if they belong to processes that are running or have run in the last 20 seconds. Active virtual pages Size of the free list Information about page faults and paging activity. These are averaged each five seconds, and given in units per second. Page reclaims (without Address translation faults (without Processes swapped in (with Processes swapped out (with Pages paged in Pages paged out Pages freed per second Anticipated short term memory shortfall Pages scanned by clock algorithm, per second Trap/interrupt rate averages per second over last 5 seconds. Device interrupts per second (nonclock) System calls per second CPU context switch rate (switches/sec) Breakdown of percentage usage of CPU time for the active processors User time for normal and low priority processes System time CPU idle EXAMPLES
The following examples show the output for various command options. For formatting purposes, some leading blanks have been deleted. 1. Display the default output. 2. Add the disk tranfer information to the default output. 3. Display the default output in 80-column format. 4. Replace the page reclaims and address translation faults with process swapping in the default output. 5. Display the default output twice at five-second intervals. Note that the headers are repeated. 6. Display the default output twice in 80-column format at five-second intervals. Note that the headers are repeated. 7. Display the default output and disk transfers twice in 80-column format at five-second intervals. Note that the headers repeated. 8. Display the number of forks and pages of virtual memory since boot-up. 9. Display the counts of paging-related events. WARNINGS
Users of must not rely on the exact field widths and spacing of its output, as these will vary depending on the system, the release of HP- UX, and the data to be displayed. AUTHOR
was developed by the University of California, Berkeley and HP. SEE ALSO
iostat(1). vmstat(1)

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