1 <?xml version="1.0" encoding="utf-8"?>

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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-95840076-79F2-524B-BAF7-828260BDD923" xml:lang="en"><title>Patchable

    13 Constants: KHeapShrinkHysRatio</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <codeblock id="GUID-5053B8C4-B730-5341-98A3-801409460573" xml:space="preserve">EXPORT_C extern const TInt KHeapShrinkHysRatio;</codeblock>

    15 <table id="GUID-EA923219-CBC1-5F40-9EF3-30EE85C02F76">

    16 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

    17 <tbody>

    18 <row>

    19 <entry><p>Exported from: </p> </entry>

    20 <entry><p> <filepath>EUSER.DLL</filepath>, <filepath>EKERN.EXE</filepath>  </p> </entry>

    21 </row>

    22 <row>

    23 <entry><p>Defined in: </p> </entry>

    24 <entry><p> <filepath> .../os/kernelhwsrv/kernel/eka/common/heap.cpp</filepath>  </p> </entry>

    25 </row>

    26 <row>

    27 <entry><p>Purpose: </p> </entry>

    28 <entry><p>This constant defines the ratio that determines the amount of hysteresis

    29 between heap growing and heap shrinking. It is a 32-bit fixed point number

    30 where the radix point is defined to be between bits 7 and 8 (where the LSB

    31 is bit 0) i.e. using standard notation, a Q8 or a fx24.8 fixed point number.

    32 For example for a ratio of 2.0 set <codeph>KHeapShrinkHysRatio=0x200</codeph>. </p> <p>The

    33 heap shrinking hysteresis value is calculated to be: </p> <codeblock id="GUID-1144F94A-6B4C-582D-B1FA-E5852F6BFAA6" xml:space="preserve">KHeapShrinkHysRatio*(iGrowBy&gt;&gt;8)</codeblock> <p>where <codeph>iGrowBy</codeph> is a page aligned value set by the argument, <codeph>aGrowBy</codeph>,

    34 to the <xref href="GUID-EFAFDD75-7E59-306A-882D-317F5564979E.dita"><apiname>RHeap</apiname></xref> constructor. Default hysteresis value is <codeph>iGrowBy</codeph> bytes

    35 i.e. <codeph>KHeapShrinkHysRatio=2.0</codeph>. Memory usage may be improved

    36 by reducing the heap shrinking hysteresis by setting 1.0 &lt; <codeph>KHeapShrinkHysRatio</codeph> &lt;

    37 2.0. Heap shrinking hysteresis is disabled/removed when <codeph>KHeapShrinkHysRatio</codeph> &lt;=

    38 1.0. </p> </entry>

    39 </row>

    40 </tbody>

    41 </tgroup>

    42 </table></conbody></concept>