Sprite 1984 - 1993/Sprite 1984 - 1993.iso/man/cmds/vmstat.man

Text File | 1990-07-03 | 14.1 KB | 285 lines

' $Header: /sprite/src/cmds/vmstat/RCS/vmstat.man,v 1.3 90/07/03 16:26:45 mendel Exp $ SPRITE (Berkeley)
.so \*(]ltmac.sprite
.HS VMSTAT cmds
.BS
.SH NAME
vmstat \- print virtual memory stats
.SH SYNOPSIS
\fBvmstat \fR[\fB\-svmP\fR] [\fB\-t \fIinterval\fR] [\fB\-T \fImaxSkip\fR] [\fB\-l \fIlines\fR] [\fB\-fp \fIthreshold\fR]
.SH OPTIONS
.IP "\fB\-s\fR" 14
Print out statistics about all in-use segments instead of overall vm stats.
.IP "\fB\-v\fR" 14
Print out extra information when printing overall vm stats.
.IP "\fB\-t \fIinterval\fR" 14
Print out a line of terse vm stats every \fIinterval\fR seconds.  If
\fIinterval\fR is specified as 0 then only a single line is printed.
.IP "\fB\-m\fR" 14
Print out the number of modified pages instead of kernel stack pages when using
the \fB\-t\fR option.
.IP "\fB\-l \fInumLines\fR" 14
Print out \fInumLines\fR lines before printing the header again when
using the \fB\-t\fR option.
The default is 25 lines.
.IP "\fB\-f \fIthreshold\fR" 14
Number of page faults per second before should print out stats with
the \fB\-t\fR option.
No lines will be printed unless more than \fIthreshold\fR page faults occur
or the \fB\-p\fR or \fB\-T\fR options are in effect.
.IP "\fB\-p \fIthreshold\fR" 14
Number of page-outs per second before should print out stats with the
\fB\-t\fR option.
No lines will be printed unless more than \fIthreshold\fR page-outs occur
or the \fB\-f\fR or \fB\-T\fR options are in effect.
.IP "\fB\-T \fImaxSkip\fR" 14
Maximum number of times to skip printing out statistics because of the
\fB\-f\fR and \fB\-p\fR options.
.IP "\fB\-P\fI" 14
Print out statistics since the last time that they were printed, not
since the last interval.  Used with the \fB\-t\fR option.
.BE

.SH DESCRIPTION
.LP
This command prints out virtual memory statistics.  There are three
possible formats and types of information that are printed.
The default is to print overall virtual memory
statistics; the volume of statistics that are printed is controlled by
the \fB\-v\fR option.  If the \fB\-s\fR option is specified then statistics about
all actively used segments are printed instead.  If the \fB\-t\fR option
is specified then a terse line of information is printed at regular
intervals;  the \fB\-TlfpPm\fR options control how the data is formatted
and how often it is printed.
The next three sections describe the three printing formats in more detail.
.SH "GENERAL STATISTICS"
By default \fBvmstat\fR prints out general statistics about the virtual memory
system.  If the \fB\-v\fR option is specified then more detailed statistics
will be printed.  The normal information that is printed is divided into
5 sections: memory use, segment use, page fault statistics, page-out
statistics and copy-on-write activity.  The memory use section is titled
``MEMORY STATS'' and contains 6 lines of information with the following
titles and information:
.IP "\fIPage Size\fR" 15
The logical page size; this is a multiple of the physical page size.
.IP "\fIMemory Size\fR" 15
The amount of physical memory in Kbytes that is available on the machine.
.IP "\fIKernel Memory\fR" 15
The amount of memory in Kbytes that is being used by the kernel.  There are
four pieces of information on this line (from left to right):
the total amount of memory used by the kernel, the portion of the total
that is used for kernel
code and data, the portion used for kernel stacks and the portion that is
kept in emergency reserve.
.IP "\fIUser Memory\fR" 15
The amount of memory in Kbytes that is being used by user processes.  There
are 3 pieces of information on this line (from left to right):
the total amount of memory used by user processes, the portion of the total
that is dirty and the portion that is clean.
.IP "\fIFS Memory\fR" 15
The amount of memory in Kbytes that is being used by the file system.
The 3 pieces of information on this line are (from left to right): the
total amount of memory used by the file system, the minimum amount of memory
that has ever been used and the maximum amount that has been used.
.IP "\fIFree Memory\fR" 15
The amount of memory in Kbytes that is not being used by anyone.
.LP
The second section of statistics is entitled ``SEGMENT STATS''.  This section
contains four lines of information, one each for active code segments,
inactive code segments, heap segments and stack segments.  Each contains
the number of segments of the given type and the amount of memory in
Kbytes that is being used by the particular type of segment.
.LP
The third section of statistics is entitled ``FAULT STATS''.  The first
line contains the total number of faults.  The second line divides the
total faults into the 7 different types of faults:
.IP "\fIZero\fR" 10
Pages that are filled with zeroes.
.IP "\fIFS\fR" 10
Pages that are filled from an object file in the file system.
.IP "\fISwap\fR" 10
Pages that are filled from a swap file.
.IP "\fIQuick\fR" 10
Page faults that were handled merely by validating the page in hardware.
.IP "\fICOW\fR" 10
Copy-on-write faults.
.IP "\fICOR\fR" 10
Copy-on-reference faults.
.IP "\fICOR-mod\fR" 10
Faults that occured because pages that were filled because of copy-on-reference
faults were marked as read-only.  This is done to compare copy-on-reference
to copy-on-write (see \fIvmcmd\fR for details).
.LP
The third line divides the faults into the different segments that the
faults occured in.  The last line is the number of faults that collided with
another process faulting on the same page.
.LP
The fourth section which is entitled ``PAGE-OUTS'' contains the number of
pages that were written to swap space.
.LP
The last section is entitled ``COPY-ON-WRITE'' and contains statistics
about copy-on-write and copy-on-reference behavior.  The information in
this section is presented as the number of faults that occured divided
by the number of copy-on-write or copy-on-reference pages.  Statistics
are presented for both heap and stack segments separately (the entries
are labeled \fIHeap\fR and \fIStack\fR respectively) and for the sum
of the heap and stack statistics (labeled \fITot\fR).  The first two
lines contain information about copy-on-write (COW) behavior, the second
two about copy-on-reference (COR) behavior and the last two
about the percentage
of pages that were copied because of copy-on-reference faults that were
eventually modified (COR-mod).  The information about COW behavior contains
an additional statistic labeled \fIQuick\fR which is the number of
copy-on-write faults that were handled by merely changing the protection;
no copy was required.
.LP
When the \fB\-v\fR option is specified additional results are presented.
These results are more obscure and are probably only of interest to those who
understand the internals of the Sprite virtual memory system.  The first
additional statistic is a measurement of the need for modify bits
and is given under the ``MEMORY STATS'' section.  This line of statistics
which is labeled \fIMod page stats\fR gives three bits of information.
The first entry (labeled \fIPot-mod\fR) is the number of
page frames that were being actively used by heap and stack segments
that were taken away from the segment and given to another segment; since
these segments are writable, the pages in these segments are potentially
modified.
The second entry (labeled \fINot-mod\fR) is the number of potentially modified
pages that were clean.  The last entry (labeled
\fINot-hard-mod\fR) is the number of potentially modified pages that did
not have the hardware modify bit set; pages can be marked as modified by
the virtual memory system (e.g. zero-filled pages) even though they do not
have the modify bit set by the hardware.
.LP
The second extra set of statistics is under the ``PAGE-OUTS'' section.  The
first extra line which is labeled \fIClean-wait\fR is the number of times that
processes that were exiting had to wait because a page that they were
freeing was being cleaned.  The second line labeled \fICleaner starts\fR
is the number of times that a page cleaner was started up to write out
pages.
.LP
The remaining extra statistics that are printed with the \fB\-v\fR option
are under entirely different sections.  The first section which is
entitled ``ALLOCATION STATS'' gives statistics about the allocation of
memory.  The first line which is labeled \fIVm allocs\fR gives the
following information (from left to right): the total number of pages that
were allocated, the portion of this total that came from the free list,
the portion that came from the file system and the portion that came from
the allocate list.  The second line which is labeled \fIVM-FS stats\fR gives
statistics about the virtual memory and file system negotiation.  The
first two entries give the number
of times that the file system asked the virtual memory system for the
age of its oldest page (labeled \fIFS-asked\fR) and the number of these
times that a free page was available (labeled \fIHad-free-page\fR).
The second two entries give the number of pages that the file system added
to its cache and the number of pages that it deleted from its cache
(labeled \fIFS-map\fR and \fIFS-unmap\fR respectively).
.LP
The next two lines of statistics under the ``ALLOCATION STATS'' section
contains information about searching the memory lists.  The
first line gives how many times that the lists were searched for pages and
how many times the memory was found on the free list and how many times
it was found on the allocation list (labeled \fIFree\fR and \fIIn-use\fR
respectively).  The second line gives information about why multiple
iterations through the allocation list were required; most of the time
the first element on the list can be used.  This line contains the
following information from left to right: the total number of extra searches,
the portion of extra searches that were required because
the page frame was locked (labeled \fILock\fR), the page frame was
referenced (\fIlabeled \fIRef\fR) or the page frame was dirty
(\fIDirty\fR).
.LP
The next section of statistics is entitled ``LIST STATS''.  This
section gives the current number of pages that are
on each of the four memory list.
.LP
The next section is labeled ``PAGE MAPPING STATS''.  This section gives
the number of times a process had to wait because the fixed number of slots
that are used to map user pages into the kernel's virtual address spacce
were all in use.
.LP
The last section is entitled ``HARDWARE STATS'' and contains
information that depends on the hardware.  For Sun workstations it
contains statistics about many times one of the 8 hardware contexts had
to be taken away from one process and given to another and the number
of times that a hardware PMEG had to be taken away from one segment and
given to another. For MIPS R2000/R3000 based machines such as
DecStations, the number of times TLB pids were stolen from active processes
is reported.
.SH "SEGMENT STATISTICS"
.LP
When the \fI-s\fR option is given to \fBvmstat\fR then statistics about all
in use segments are printed.  There are 6 columns of information:
.IP \fISEG-NUM\fR 20
The segment number.
.IP \fITYPE\fR 20
The type of segment.  The segment type can be
\fIInactive\fR for inactive code segments or \fICode\fR, \fIHeap\fR  or
\fIStack\fR for the other three types of segments.
.IP \fISIZE\fR 20
The total size of the segment's virtual addres space in Kbytes.
.IP \fIRES-SIZE\fR 20
The amount of physical memory occupied by the segment in Kbytes.
.IP \fINUM-REFS\fR 20
The number of processes that are actively using this segment.
.IP \fIOBJECT-FILE-NAME\fR 20
The name of the object file that the code segment is being demand loaded
from.
.LP
After the information about each individual segment is printed a summary
of the segment information is printed.
.SH "STATISTICS AT REGULAR INTERVALS"
.LP
If the \fB\-t \fIinterval\fR option is given to \fBvmstat\fR then a line of
terse statistics is printed out at regular intervals.  If \fIinterval\fR is 0
then only a single line of statistics is printed.  If \fIinterval\fR is
greater than 0 then a line of statistics is printed out every
\fIinterval\fR seconds.  If the \fB\-f \fIfaultThreshold\fR and/or
\fB\-p \fIpageoutThreshold\fR options are used then statistics will be
checked every \fIinterval\fR seconds but only will be printed out
if the number of page faults in the last interval is greater than
\fIfaultThreshold\fR or the number of pageouts is greater than
\fIpageoutThreshold\fR.  If the \fB\-T \fImaxSkip\fR option is used then
statistics will be printed out at least every \fImaxSkip\fR intervals
regardless whether or not enough page-outs or page faults have occured.
.LP
All memory use statistics are printed in units of 1024 bytes.
Each line contains 10 columns of information:
.IP \fIAVAIL\fR 10
The total amount of physical memory available.
.IP \fIFREE\fR 10
The amount of memory that is not being used by anyone.
.IP \fIUSER\fR 10
The amount of memory that is being used by user processes.
.IP \fIKMEM\fR 10
The amount of memory that is being used by the kernel for code and data.
.IP \fIKSTK\fR 10
The amount of memory that is being used for kernel stacks.
.IP \fIFS$\fR 10
The size of the file system cache.
.IP \fIPF-NUM\fR 10
The number of page faults that have occured.
.IP \fIPF-SWP\fR 10
The number of page faults that were filled from swap space.
.IP \fIPF-FS\fR 10
The number of page faults that were filled from the file system.
.IP \fIPOUTS\fR 10
The number of pages that were written to swap space.
.LP
If the \fB\-m\fR option is specified then the \fIKSTK\fR column will be
replaced by a column labeled \fIMOD%\fR which contains the percentage
of user memory that is modified.  The number of kernel stack pages
will be added into the statistics under the \fIKMEM\fR column.
.LP
By default a new column header line will be printed after 25 lines of
output.  The \fB\-l \fIlines\fR option can be used to force the header line
to be printed after \fIlines\fR lines of output are printed.
.LP
The number of page faults and page-outs that are printed are by default
the number since the last interval.  However, many intervals can
be skipped because of the \fB\-f\fR and \fB\-p\fR options.  The
\fB\-P\fR option will force \fBvmstat\fR to print out the number of faults and
pageouts since the last time that a line was printed instead of since the
last interval.
.SH KEYWORDS
virtual memory, statistics