b05cfacb3d
1998-08-12 Martin Baulig <martin@home-of-linux.org> * features: New directory. * gnome-hackers.sgml: Updated documentation.
103 lines
3.4 KiB
Plaintext
103 lines
3.4 KiB
Plaintext
<para>
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The automatically generated description above is taken from the
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manual page of the <filename>/proc</filename> filesystem under Linux
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and is a little bit confusing, so I make this clear here.
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<note>
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<title>Note for people porting &libgtop; to other systems</title>
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<para>
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Well, every operating system has its own idea about the memory usage
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of a processes, and also system utilities like <filename>ps</filename>
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show different things on different systems.
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<para>
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Nevertheless, we should try to make &libgtop; as system independent
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as possible, so I give you some hints here how &glibtop-get-procmem;
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should work.
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<itemizedlist>
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<listitem>
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<para>
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When you use &mmap; with either &MAP-SHARED; or &MAP-PRIVATE;,
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this should only affect the &pmem-vsize; of the process and
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none of its &pmem-size;, &pmem-resident;, &pmem-shared; and
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&pmem-rss; sizes.
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<listitem>
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<para>
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As soon as you read some of the &mmap;ed pages, they will be
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demand-loaded and thus count towards the &pmem-size; of the
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process. Also - we assume there is enough free memory - they
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are resident in memory until they get stolen or swapped out
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and thus increase the &pmem-resident; and &pmem-rss; sizes of
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the process.
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<listitem>
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<para>
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If the process has used &MAP-SHARED; and another process
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attaches the same file also &MAP-SHARED; some of the pages
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are shared with this process and thus increase the &pmem-shared;
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sizes of both processes.
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<listitem>
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<para>
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If the process has used &MAP-PRIVATE; and writes to the &mmap;ed
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pages, the only difference to reading from them is that they
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get dirty and cannot be stolen any longer but will get swapped
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out.
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<listitem>
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<para>
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If memory gets rare, clean pages are normally stolen which
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decreases the &pmem-size;, &pmem-resident;, &pmem-shared; and
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&pmem-rss; sizes of the process.
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<listitem>
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<para>
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When dirty pages are swapped out, this will
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<emphasis>not</emphasis> decrease the &pmem-size; of the
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process but only its &pmem-resident; and &pmem-rss; sizes
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(dirty pages cannot be shared).
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<listitem>
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<para>
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The &pmem-vsize; of a process can <emphasis>only</emphasis>
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be changed by the process itself when it requests or frees
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memory but <emphasis>never</emphasis> due to swapping
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activity of the system.
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<listitem>
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<para>
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If the &pmem-shared; size changes, this
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<emphasis>only</emphasis> means that the number of pages that
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are currently shared with other processes has changed; if this
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happens, this will <emphasis>never</emphasis> affect any of the
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other sizes of the process.
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</itemizedlist>
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</note>
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<para>
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The hints above describe how it works under Linux - and we should try to
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make &glibtop-get-procmem; show the same behavior under every other
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system.
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<para>
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If you want to make any comments, flames, suggestions about this, please
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feel free to do so.
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<!--
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Local Variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:2
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sgml-indent-data: t
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sgml-parent-document: ("../gnome-hackers.sgml" "book" "sect1" "")
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End:
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-->
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