95 lines
6.5 KiB
HTML
95 lines
6.5 KiB
HTML
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<meta name="DC.Title" content="Memory pool activity level" />
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<meta name="abstract" content="The activity level of a memory pool is the number of threads that can actively use the CPU at the same time in a memory pool. This allows for efficient use of system resources. The system manages the control of the activity level." />
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<title>Memory pool activity level</title>
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</head>
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<body id="rzaksmempoolactlevel"><a name="rzaksmempoolactlevel"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Memory pool activity level</h1>
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<div><p>The activity level of a memory pool is the number of threads that
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can actively use the CPU at the same time in a memory pool. This allows for
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efficient use of system resources. The system manages the control of the activity
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level. </p>
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<p> Often during processing in a thread, a program waits for a system resource
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or a response from a workstation user. During such waits, a thread gives up
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its use of the memory pool activity level so that another thread that is ready
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to be processed can take its place.</p>
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<p>When more threads are started than can run at the same time the excess
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threads must wait to use the processing unit (normally this wait is short).
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The memory pool activity level lets you limit the amount of main memory contention
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in the various memory pools in your subsystems.</p>
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<p>The number of threads running (or active threads) refers to the number
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of threads that are eligible to compete for the processor and that count against
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the activity level for a memory pool. In this sense, active threads do not
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include threads that are waiting for input, for a message, for a device to
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be allocated, or for a file to be opened. Active threads do not include threads
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that are ineligible (threads that are ready to run but the memory pool activity
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level is at its maximum).</p>
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<div class="section"><h4 class="sectiontitle">How activity levels work</h4><p>More than one thread can
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be active at the same time in a memory pool because the processing for a thread
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can be briefly interrupted while needed data is retrieved from auxiliary storage.
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During this delay, which is typically short, another thread can run. Using
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the activity level, the machine can process a large number of threads in a
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memory pool and at the same time hold the level of contention to the limit
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that you specify.</p>
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<dl><dt class="dlterm">Maximum activity level</dt>
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<dd>After the maximum activity level for a memory pool has been
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reached, additional threads needing the memory pool are placed in the ineligible
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state to wait for the number of active threads in the memory pool to fall
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below the maximum activity level or for a thread to reach the end of its time
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slice. As soon as a thread gives up its use of the memory pool, the other
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threads that are not active become eligible to run by their priority. For
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example, if a running thread is waiting for a response from a workstation,
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it gives up its activity level and the activity level is no longer at its
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maximum.<p> </p>
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</dd>
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<dt class="dlterm">Defining memory pool activity levels</dt>
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<dd>Defining memory pools and activity levels correctly is generally dependent
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on size of the memory pool, the number of CPUs, the number of disk unit arms,
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and the characteristics of the application.</dd>
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</dl>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaksaboutmempools.htm" title="A memory pool is a logical division of main memory or storage that is reserved for processing a job or group of jobs. On the iSeries server, all main storage can be divided into logical allocations called memory pools. By default, the system manages the transfer of data and programs into memory pools.">Memory pools</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="rzaksdispmempool.htm" title="You can view information about the memory pools that are on your system by using iSeries Navigator or the character-based interface.">View memory pool information</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../rzahx/rzahxmngparent.htm">Manage iSeries performance</a></div>
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<div><a href="../rzahx/rzahxtune.htm">Basic performance tuning</a></div>
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<div><a href="../rzahx/rzahxapsparent.htm">Applications for performance management</a></div>
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<div><a href="../experience/work3abstract.htm">Experience report: The Performance Adjuster</a></div>
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</div>
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</div>
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</body>
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</html>
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