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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head><meta http-equiv="content-type" content="text/html; charset=UTF-8" /><title>CachedBufferAllocator xref</title><link type="text/css" rel="stylesheet" href="../../../../stylesheet.css" /></head><body><div id="overview"><a href="../../../../../apidocs/org/apache/mina/common/CachedBufferAllocator.html">View Javadoc</a></div><pre><a name="1" href="#1">1</a> <em class="jxr_comment">/*</em><a name="2" href="#2">2</a> <em class="jxr_comment"> * Licensed to the Apache Software Foundation (ASF) under one</em><a name="3" href="#3">3</a> <em class="jxr_comment"> * or more contributor license agreements. See the NOTICE file</em><a name="4" href="#4">4</a> <em class="jxr_comment"> * distributed with this work for additional information</em><a name="5" href="#5">5</a> <em class="jxr_comment"> * regarding copyright ownership. The ASF licenses this file</em><a name="6" href="#6">6</a> <em class="jxr_comment"> * to you under the Apache License, Version 2.0 (the</em><a name="7" href="#7">7</a> <em class="jxr_comment"> * "License"); you may not use this file except in compliance</em><a name="8" href="#8">8</a> <em class="jxr_comment"> * with the License. You may obtain a copy of the License at</em><a name="9" href="#9">9</a> <em class="jxr_comment"> *</em><a name="10" href="#10">10</a> <em class="jxr_comment"> * <a href="http://www.apache.org/licenses/LICENSE-2.0" target="alexandria_uri">http://www.apache.org/licenses/LICENSE-2.0</a></em><a name="11" href="#11">11</a> <em class="jxr_comment"> *</em><a name="12" href="#12">12</a> <em class="jxr_comment"> * Unless required by applicable law or agreed to in writing,</em><a name="13" href="#13">13</a> <em class="jxr_comment"> * software distributed under the License is distributed on an</em><a name="14" href="#14">14</a> <em class="jxr_comment"> * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY</em><a name="15" href="#15">15</a> <em class="jxr_comment"> * KIND, either express or implied. See the License for the</em><a name="16" href="#16">16</a> <em class="jxr_comment"> * specific language governing permissions and limitations</em><a name="17" href="#17">17</a> <em class="jxr_comment"> * under the License.</em><a name="18" href="#18">18</a> <em class="jxr_comment"> *</em><a name="19" href="#19">19</a> <em class="jxr_comment"> */</em><a name="20" href="#20">20</a> <strong class="jxr_keyword">package</strong> org.apache.mina.common;<a name="21" href="#21">21</a> <a name="22" href="#22">22</a> <strong class="jxr_keyword">import</strong> java.nio.ByteBuffer;<a name="23" href="#23">23</a> <strong class="jxr_keyword">import</strong> java.nio.ByteOrder;<a name="24" href="#24">24</a> <strong class="jxr_keyword">import</strong> java.util.HashMap;<a name="25" href="#25">25</a> <strong class="jxr_keyword">import</strong> java.util.Map;<a name="26" href="#26">26</a> <strong class="jxr_keyword">import</strong> java.util.Queue;<a name="27" href="#27">27</a> <a name="28" href="#28">28</a> <strong class="jxr_keyword">import</strong> org.apache.mina.util.CircularQueue;<a name="29" href="#29">29</a> <a name="30" href="#30">30</a> <em class="jxr_javadoccomment">/**</em><a name="31" href="#31">31</a> <em class="jxr_javadoccomment"> * An {@link IoBufferAllocator} that caches the buffers which are likely to</em><a name="32" href="#32">32</a> <em class="jxr_javadoccomment"> * be reused during auto-expansion of the buffers.</em><a name="33" href="#33">33</a> <em class="jxr_javadoccomment"> * <p></em><a name="34" href="#34">34</a> <em class="jxr_javadoccomment"> * In {@link SimpleBufferAllocator}, the underlying {@link ByteBuffer} of</em><a name="35" href="#35">35</a> <em class="jxr_javadoccomment"> * the {@link IoBuffer} is reallocated on its capacity change, which means</em><a name="36" href="#36">36</a> <em class="jxr_javadoccomment"> * the newly allocated bigger {@link ByteBuffer} replaces the old small</em><a name="37" href="#37">37</a> <em class="jxr_javadoccomment"> * {@link ByteBuffer}. Consequently, the old {@link ByteBuffer} is marked</em><a name="38" href="#38">38</a> <em class="jxr_javadoccomment"> * for garbage collection.</em><a name="39" href="#39">39</a> <em class="jxr_javadoccomment"> * <p></em><a name="40" href="#40">40</a> <em class="jxr_javadoccomment"> * It's not a problem in most cases as long as the capacity change doesn't</em><a name="41" href="#41">41</a> <em class="jxr_javadoccomment"> * happen frequently. However, once it happens too often, it burdens the</em><a name="42" href="#42">42</a> <em class="jxr_javadoccomment"> * VM and the cost of filling the newly allocated {@link ByteBuffer} with</em><a name="43" href="#43">43</a> <em class="jxr_javadoccomment"> * {@code NUL} surpass the cost of accessing the cache. In 2 dual-core</em><a name="44" href="#44">44</a> <em class="jxr_javadoccomment"> * Opteron Italy 270 processors, {@link CachedBufferAllocator} outperformed</em><a name="45" href="#45">45</a> <em class="jxr_javadoccomment"> * {@link SimpleBufferAllocator} in the following situation:</em><a name="46" href="#46">46</a> <em class="jxr_javadoccomment"> * <ul></em><a name="47" href="#47">47</a> <em class="jxr_javadoccomment"> * <li>when a 32 bytes buffer is expanded 4 or more times,</li> </em><a name="48" href="#48">48</a> <em class="jxr_javadoccomment"> * <li>when a 64 bytes buffer is expanded 4 or more times,</li></em><a name="49" href="#49">49</a> <em class="jxr_javadoccomment"> * <li>when a 128 bytes buffer is expanded 2 or more times,</li></em><a name="50" href="#50">50</a> <em class="jxr_javadoccomment"> * <li>and when a 256 bytes or bigger buffer is expanded 1 or more times.</li></em><a name="51" href="#51">51</a> <em class="jxr_javadoccomment"> * </ul></em><a name="52" href="#52">52</a> <em class="jxr_javadoccomment"> * Please note the observation above is subject to change in a different</em><a name="53" href="#53">53</a> <em class="jxr_javadoccomment"> * environment.</em><a name="54" href="#54">54</a> <em class="jxr_javadoccomment"> * <p></em><a name="55" href="#55">55</a> <em class="jxr_javadoccomment"> * {@link CachedBufferAllocator} uses {@link ThreadLocal} to store the cached</em><a name="56" href="#56">56</a> <em class="jxr_javadoccomment"> * buffer, allocates buffers whose capacity is power of 2 only and provides</em><a name="57" href="#57">57</a> <em class="jxr_javadoccomment"> * performance advantage if {@link IoBuffer#free()} is called properly.</em><a name="58" href="#58">58</a> <em class="jxr_javadoccomment"> *</em><a name="59" href="#59">59</a> <em class="jxr_javadoccomment"> * @author The Apache MINA Project (dev@mina.apache.org)</em><a name="60" href="#60">60</a> <em class="jxr_javadoccomment"> * @version $Rev: 594400 $, $Date: 2007-11-12 19:49:43 -0700 (Mon, 12 Nov 2007) $</em><a name="61" href="#61">61</a> <em class="jxr_javadoccomment"> */</em><a name="62" href="#62">62</a> <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">class</strong> <a href="../../../../org/apache/mina/common/CachedBufferAllocator.html">CachedBufferAllocator</a> implements <a href="../../../../org/apache/mina/common/IoBufferAllocator.html">IoBufferAllocator</a> {<a name="63" href="#63">63</a> <a name="64" href="#64">64</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> DEFAULT_MAX_POOL_SIZE = 8;<a name="65" href="#65">65</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> DEFAULT_MAX_CACHED_BUFFER_SIZE = 1 << 18; <em class="jxr_comment">// 256KB</em><a name="66" href="#66">66</a> <a name="67" href="#67">67</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> maxPoolSize;<a name="68" href="#68">68</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> maxCachedBufferSize;<a name="69" href="#69">69</a> <a name="70" href="#70">70</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> ThreadLocal<Map<Integer, Queue<CachedBuffer>>> heapBuffers;<a name="71" href="#71">71</a> <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">final</strong> ThreadLocal<Map<Integer, Queue<CachedBuffer>>> directBuffers;<a name="72" href="#72">72</a> <a name="73" href="#73">73</a> <em class="jxr_javadoccomment">/**</em><a name="74" href="#74">74</a> <em class="jxr_javadoccomment"> * Creates a new instance with the default parameters</em><a name="75" href="#75">75</a> <em class="jxr_javadoccomment"> * ({@literal #DEFAULT_MAX_POOL_SIZE} and {@literal #DEFAULT_MAX_CACHED_BUFFER_SIZE}). </em><a name="76" href="#76">76</a> <em class="jxr_javadoccomment"> */</em><a name="77" href="#77">77</a> <strong class="jxr_keyword">public</strong> <a href="../../../../org/apache/mina/common/CachedBufferAllocator.html">CachedBufferAllocator</a>() {<a name="78" href="#78">78</a> <strong class="jxr_keyword">this</strong>(DEFAULT_MAX_POOL_SIZE, DEFAULT_MAX_CACHED_BUFFER_SIZE);<a name="79" href="#79">79</a> }<a name="80" href="#80">80</a> <a name="81" href="#81">81</a> <em class="jxr_javadoccomment">/**</em><a name="82" href="#82">82</a> <em class="jxr_javadoccomment"> * Creates a new instance.</em><a name="83" href="#83">83</a> <em class="jxr_javadoccomment"> * </em><a name="84" href="#84">84</a> <em class="jxr_javadoccomment"> * @param maxPoolSize the maximum number of buffers with the same capacity per thread.</em><a name="85" href="#85">85</a> <em class="jxr_javadoccomment"> * <tt>0</tt> disables this limitation.</em><a name="86" href="#86">86</a> <em class="jxr_javadoccomment"> * @param maxCachedBufferSize the maximum capacity of a cached buffer.</em><a name="87" href="#87">87</a> <em class="jxr_javadoccomment"> * A buffer whose capacity is bigger than this value is</em><a name="88" href="#88">88</a> <em class="jxr_javadoccomment"> * not pooled. <tt>0</tt> disables this limitation.</em><a name="89" href="#89">89</a> <em class="jxr_javadoccomment"> */</em><a name="90" href="#90">90</a> <strong class="jxr_keyword">public</strong> <a href="../../../../org/apache/mina/common/CachedBufferAllocator.html">CachedBufferAllocator</a>(<strong class="jxr_keyword">int</strong> maxPoolSize, <strong class="jxr_keyword">int</strong> maxCachedBufferSize) {<a name="91" href="#91">91</a> <strong class="jxr_keyword">if</strong> (maxPoolSize < 0) {<a name="92" href="#92">92</a> <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"maxPoolSize: "</span> + maxPoolSize);<a name="93" href="#93">93</a> }<a name="94" href="#94">94</a> <strong class="jxr_keyword">if</strong> (maxCachedBufferSize < 0) {<a name="95" href="#95">95</a> <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"maxCachedBufferSize: "</span> + maxCachedBufferSize);<a name="96" href="#96">96</a> }<a name="97" href="#97">97</a> <a name="98" href="#98">98</a> <strong class="jxr_keyword">this</strong>.maxPoolSize = maxPoolSize;<a name="99" href="#99">99</a> <strong class="jxr_keyword">this</strong>.maxCachedBufferSize = maxCachedBufferSize;<a name="100" href="#100">100</a> <a name="101" href="#101">101</a> <strong class="jxr_keyword">this</strong>.heapBuffers = <strong class="jxr_keyword">new</strong> ThreadLocal<Map<Integer, Queue<CachedBuffer>>>() {<a name="102" href="#102">102</a> @Override<a name="103" href="#103">103</a> <strong class="jxr_keyword">protected</strong> Map<Integer, Queue<CachedBuffer>> initialValue() {<a name="104" href="#104">104</a> <strong class="jxr_keyword">return</strong> newPoolMap();<a name="105" href="#105">105</a> }<a name="106" href="#106">106</a> };<a name="107" href="#107">107</a> <strong class="jxr_keyword">this</strong>.directBuffers = <strong class="jxr_keyword">new</strong> ThreadLocal<Map<Integer, Queue<CachedBuffer>>>() {<a name="108" href="#108">108</a> @Override<a name="109" href="#109">109</a> <strong class="jxr_keyword">protected</strong> Map<Integer, Queue<CachedBuffer>> initialValue() {<a name="110" href="#110">110</a> <strong class="jxr_keyword">return</strong> newPoolMap();<a name="111" href="#111">111</a> }<a name="112" href="#112">112</a> };<a name="113" href="#113">113</a> }<a name="114" href="#114">114</a> <a name="115" href="#115">115</a> <em class="jxr_javadoccomment">/**</em><a name="116" href="#116">116</a> <em class="jxr_javadoccomment"> * Returns the maximum number of buffers with the same capacity per thread.</em><a name="117" href="#117">117</a> <em class="jxr_javadoccomment"> * <tt>0</tt> means 'no limitation'.</em><a name="118" href="#118">118</a> <em class="jxr_javadoccomment"> */</em><a name="119" href="#119">119</a> <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> getMaxPoolSize() {<a name="120" href="#120">120</a> <strong class="jxr_keyword">return</strong> maxPoolSize;<a name="121" href="#121">121</a> }<a name="122" href="#122">122</a> <a name="123" href="#123">123</a> <em class="jxr_javadoccomment">/**</em><a name="124" href="#124">124</a> <em class="jxr_javadoccomment"> * Returns the maximum capacity of a cached buffer. A buffer whose</em><a name="125" href="#125">125</a> <em class="jxr_javadoccomment"> * capacity is bigger than this value is not pooled. <tt>0</tt> means</em><a name="126" href="#126">126</a> <em class="jxr_javadoccomment"> * 'no limitation'.</em><a name="127" href="#127">127</a> <em class="jxr_javadoccomment"> */</em><a name="128" href="#128">128</a> <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> getMaxCachedBufferSize() {<a name="129" href="#129">129</a> <strong class="jxr_keyword">return</strong> maxCachedBufferSize;<a name="130" href="#130">130</a> }<a name="131" href="#131">131</a> <a name="132" href="#132">132</a> <strong class="jxr_keyword">private</strong> Map<Integer, Queue<CachedBuffer>> newPoolMap() {<a name="133" href="#133">133</a> Map<Integer, Queue<CachedBuffer>> poolMap =<a name="134" href="#134">134</a> <strong class="jxr_keyword">new</strong> HashMap<Integer, Queue<CachedBuffer>>();<a name="135" href="#135">135</a> <strong class="jxr_keyword">int</strong> poolSize = maxPoolSize == 0? DEFAULT_MAX_POOL_SIZE : maxPoolSize;<a name="136" href="#136">136</a> <strong class="jxr_keyword">for</strong> (<strong class="jxr_keyword">int</strong> i = 0; i < 31; i ++) {<a name="137" href="#137">137</a> poolMap.put(1 << i, <strong class="jxr_keyword">new</strong> CircularQueue<CachedBuffer>(poolSize));<a name="138" href="#138">138</a> }<a name="139" href="#139">139</a> poolMap.put(0, <strong class="jxr_keyword">new</strong> CircularQueue<CachedBuffer>(poolSize));<a name="140" href="#140">140</a> poolMap.put(Integer.MAX_VALUE, <strong class="jxr_keyword">new</strong> CircularQueue<CachedBuffer>(poolSize));⌨️ 快捷键说明
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