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<?xml version="1.0"?> |
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|
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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|
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<refentry id="get_diskio_stats"> |
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|
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<refentryinfo> |
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<date>$Date: 2003/11/21 09:24:53 $</date> |
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<releaseinfo>$Id: get_diskio_stats.xml,v 1.4 2003/11/21 09:24:53 tdb Exp $</releaseinfo> |
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</refentryinfo> |
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|
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<refmeta> |
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<refentrytitle>get_diskio_stats</refentrytitle> |
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<manvolnum>3</manvolnum> |
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<refmiscinfo>i-scream</refmiscinfo> |
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</refmeta> |
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|
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<refnamediv> |
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<refname>get_diskio_stats</refname> |
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<refname>get_diskio_stats_diff</refname> |
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<refpurpose>get disk io statistics</refpurpose> |
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</refnamediv> |
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|
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<refsynopsisdiv> |
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<funcsynopsis> |
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<funcsynopsisinfo>#include <statgrab.h></funcsynopsisinfo> |
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<funcprototype> |
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<funcdef>diskio_stat_t *<function>get_diskio_stats</function></funcdef> |
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<paramdef>int *<parameter>entries</parameter></paramdef> |
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</funcprototype> |
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<funcprototype> |
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<funcdef>diskio_stat_t *<function>get_diskio_stats_diff</function></funcdef> |
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<paramdef>int *<parameter>entries</parameter></paramdef> |
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</funcprototype> |
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</funcsynopsis> |
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</refsynopsisdiv> |
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|
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<refsect1> |
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<title>Description</title> |
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<para> |
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Both calls take a pointer to an int, |
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<parameter>entries</parameter>, which is filled with the number |
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of disks the machine has. This is needed to know how many |
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<structname>diskio_stat_t</structname> structures have been |
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returned. A pointer is returned to the first |
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<structname>diskio_stat_t</structname>. |
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</para> |
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<para> |
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<function>get_diskio_stats</function> returns the disk IO stored |
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in the kernel which holds the amount of data transferred since |
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bootup. On some platforms, such as Solaris 7, this value is |
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stored in a 32bit int, so wraps around when it reaches 4GB. Other |
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platforms, such as Solaris 8, hold the value in a 64bit int, |
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which wraps somewhere near 17 million terabytes. |
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</para> |
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<para> |
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<function>get_diskio_stats_diff</function> is the same as |
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<function>get_diskio_stats</function> except it will return the |
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difference since the last call. So, for instance a call to |
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<function>get_diskio_stats_diff</function> is made, and called |
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again 5 seconds later. Over that time, 2000 bytes of traffic were |
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written and 10000 bytes read. <parameter>write_bytes</parameter> |
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will store 2000 bytes, <parameter>read_bytes</parameter> will |
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store 10000, and <parameter>systime</parameter> will store 5. |
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This function copes with wrap arounds by the O/S so should be |
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seemless to use. |
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</para> |
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<para> |
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On Solaris libstatgrab will attempt to get the cXtXdXsX |
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representation for the <varname>disk_name</varname> string. If |
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it fails it will use a name like sd0. On some systems programs |
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calling libstatgrab will need elevated privileges to lookup |
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some of the names. The mappings are built up when |
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<function>statgrab_init</function> is called. |
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</para> |
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</refsect1> |
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|
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<refsect1> |
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<title>Return Values</title> |
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|
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<para> |
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All diskio statistics return a pointer to a structure of type |
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<structname>diskio_stat_t</structname>. |
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</para> |
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|
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<programlisting> |
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typedef struct{ |
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char *disk_name; |
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long long read_bytes; |
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long long write_bytes; |
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time_t systime; |
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}diskio_stat_t; |
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</programlisting> |
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|
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<variablelist> |
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<varlistentry> |
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<term> |
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<structfield>disk_name</structfield> |
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</term> |
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<listitem> |
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<para> |
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The name known to the operating system. |
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(eg. on linux it might be hda) |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term> |
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<structfield>read_bytes</structfield> |
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</term> |
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<listitem> |
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<para> |
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The number of bytes the disk has read. |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term> |
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<structfield>write_bytes</structfield> |
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</term> |
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<listitem> |
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<para> |
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The number of bytes the disk has written. |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term> |
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<structfield>systime</structfield> |
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</term> |
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<listitem> |
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<para> |
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The time period over which <parameter>read_bytes</parameter> |
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and <parameter>write_bytes</parameter> were transferred. |
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</para> |
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</listitem> |
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</varlistentry> |
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</variablelist> |
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</refsect1> |
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|
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<refsect1> |
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<title>Bugs</title> |
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<para> |
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On the very first call <function>get_diskio_stats_diff</function> |
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will return the same as <function>get_diskio_stats</function>. |
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After the first call it will always return the difference. |
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</para> |
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<para> |
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On operating systems that hold only 32bits of data there is a |
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problem if the values wrap twice. For example, on Solaris 7 if |
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9GB is transferred and the operating system wraps at 4GB, the |
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<function>get_diskio_stats_diff</function> function will return |
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5GB. |
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</para> |
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</refsect1> |
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|
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<refsect1> |
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<title>See Also</title> |
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|
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<simplelist type="inline"> |
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<member> |
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<citerefentry> |
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<refentrytitle>statgrab</refentrytitle> |
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<manvolnum>3</manvolnum> |
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</citerefentry> |
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</member> |
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</simplelist> |
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</refsect1> |
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|
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<refsect1> |
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<title>Website</title> |
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|
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<simplelist type="vert"> |
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<member> |
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<ulink url="http://www.i-scream.org/libstatgrab/"> |
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http://www.i-scream.org/libstatgrab/ |
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</ulink> |
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</member> |
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</simplelist> |
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</refsect1> |
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|
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</refentry> |
