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<article>
<header class="page-header">
<h1 class="entry-title"><a href="/blog/2014/03/31/sigpnd-sigblk-sigign-sigcgt-in-proc-status-file/">SigPnd, ShdPnd, SigBlk, SigIgn and SigCgt Fields in Proc Information File System</a></h1>
<p class="meta">
<time datetime="2014-03-31T05:59:51-07:00" pubdate data-updated="true">Mar 31<span>st</span>, 2014</time>
</p>
</header>
<div class="entry-content"><p>The following is the field definition from Linux man proc(5).</p>
<blockquote><p>SigPnd, ShdPnd: Number of signals pending for thread and for process as a whole (see pthreads(7) and signal(7)).</p>
<p>SigBlk, SigIgn, SigCgt: Masks indicating signals being blocked, ignored, and caught (see signal(7)).</p></blockquote>
<p>But what they look like and how to interpret? Here is an output example:</p>
<blockquote><p>SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: fffffffe7ffbfeff
SigIgn: 0000000000000000
SigCgt: 0000000000000000</p></blockquote>
<p>They are displayed in hex format as 8 bytes. The right most 4 bytes represent stardard signals, the left is Linux real-time signal extension. Each bit in the 8 bytes represents one corresponding signal. If the bits index starts from zero(the right most bit in the above), The corresponding signal is represented by bit[signalValue-1]. An example is that the signal SIGHUP, whose value is 1, is represented the bit 0.</p>
<p>Take the above SigBlk as example, the first two bytes are</p>
<blockquote><p>0xfeff</p></blockquote>
<p>The binary format is</p>
<blockquote><p>1111,1110,1111,1111</p></blockquote>
<p>It means all signals from 1 to 16 are blocked except the signal 9 (SIGKILL). This is true because SIGKILL cannot be blocked or ignored.</p>
</div>
</article>
<article>
<header class="page-header">
<h1 class="entry-title"><a href="/blog/2014/03/23/oprofile-and-cache-an-experiment/">Oprofile and Memory Cache - an Experiment</a></h1>
<p class="meta">
<time datetime="2014-03-23T20:03:38-07:00" pubdate data-updated="true">Mar 23<span>rd</span>, 2014</time>
</p>
</header>
<div class="entry-content"><p>Last week, I did a small experiment of using oprofile to profile two piece of code. In this small experiment, I learned some basic ideas of using oprofile. In particular, I used oprofile to profile memory cache behaviour and the performance effect. In this experiment, I got ideas of how memory cache invalidation can affect the speed of running program. The following is the detail.</p>
<h3>The Experiment Configuration</h3>
<p>I ran the experiment in an Thinkpad T400 with a Ubuntu installation. The experiment needs to run on a multi-core processor because of profiling memory cache invalidation cost. In a single core processor, there is no such memory cache invalidation cost.</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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</pre></td><td class='code'><pre><code class=''><span class='line'>$sudo lsb_release -a
</span><span class='line'>No LSB modules are available.
</span><span class='line'>Distributor ID: Ubuntu
</span><span class='line'>Description: Ubuntu 12.04 LTS
</span><span class='line'>Release: 12.04
</span><span class='line'>Codename: precise
</span><span class='line'>
</span><span class='line'>$ cat /proc/cpuinfo |grep "model name"
</span><span class='line'>model name : Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
</span><span class='line'>model name : Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz</span></code></pre></td></tr></table></div></figure>
<h3>Source Code</h3>
<p>There are two pieces of programs, which are “no_alignment” and “alignment”. They are compiled with GNU GCC. Each program clones a child sharing the same memory address space, which means the parent and the child updating different fileds of the same global data. The difference is that the program “alignment” optimizing the fields of the shared_data to the cache line size alignment. In this way, the two fields are able to be fetched on different cache lines. Therefore, when the parent and the child runs on different cores, the “no_alignment” program has the cache invlidation costs between two cores, but the “alignment” program doesn’t.</p>
<p>The following are the source codes of the two programs. The only difference is the definition of struct shared_data.</p>
<figure class='code'><figcaption><span>no_alignment</span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
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</pre></td><td class='code'><pre><code class='c'><span class='line'><span class="cp">#define _GNU_SOURCE</span>
</span><span class='line'><span class="cp">#include <sched.h></span>
</span><span class='line'><span class="cp">#include <stdio.h></span>
</span><span class='line'><span class="cp">#include <errno.h></span>
</span><span class='line'><span class="cp">#include <stdlib.h></span>
</span><span class='line'>
</span><span class='line'><span class="c1">// shared data</span>
</span><span class='line'><span class="k">struct</span> <span class="n">shared_data</span> <span class="p">{</span>
</span><span class='line'> <span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">num_proc1</span><span class="p">;</span>
</span><span class='line'> <span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">num_proc2</span><span class="p">;</span>
</span><span class='line'><span class="p">};</span>
</span><span class='line'>
</span><span class='line'><span class="k">struct</span> <span class="n">shared_data</span> <span class="n">shared</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="c1">// define loops to run for a while</span>
</span><span class='line'><span class="kt">int</span> <span class="n">loop_i</span> <span class="o">=</span> <span class="mi">100000</span><span class="p">,</span> <span class="n">loop_j</span> <span class="o">=</span> <span class="mi">100000</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">child</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'><span class="cp">#define STACK_SIZE (8 * 1024)</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'> <span class="n">pid_t</span> <span class="n">pid</span><span class="p">;</span>
</span><span class='line'> <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* Stack */</span>
</span><span class='line'> <span class="kt">char</span> <span class="o">*</span><span class="n">stack</span> <span class="o">=</span> <span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">STACK_SIZE</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">perror</span><span class="p">(</span><span class="s">"malloc"</span><span class="p">);</span>
</span><span class='line'> <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">printf</span><span class="p">(</span><span class="s">"main: shared %p %p</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="p">,</span> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* clone a thread sharing memory space with the parent process */</span>
</span><span class='line'> <span class="k">if</span> <span class="p">((</span><span class="n">pid</span> <span class="o">=</span> <span class="n">clone</span><span class="p">(</span><span class="n">child</span><span class="p">,</span> <span class="n">stack</span> <span class="o">+</span> <span class="n">STACK_SIZE</span><span class="p">,</span> <span class="n">CLONE_VM</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">))</span> <span class="o"><</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">perror</span><span class="p">(</span><span class="s">"clone"</span><span class="p">);</span>
</span><span class='line'> <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">loop_i</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">for</span><span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o"><</span> <span class="n">loop_j</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="o">++</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">child</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="n">arg</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'> <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="n">printf</span><span class="p">(</span><span class="s">"child: shared %p %p</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="p">,</span> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">loop_i</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o"><</span> <span class="n">loop_j</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="o">++</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>
<figure class='code'><figcaption><span>alignment</span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
<span class='line-number'>37</span>
<span class='line-number'>38</span>
<span class='line-number'>39</span>
<span class='line-number'>40</span>
<span class='line-number'>41</span>
<span class='line-number'>42</span>
<span class='line-number'>43</span>
<span class='line-number'>44</span>
<span class='line-number'>45</span>
<span class='line-number'>46</span>
<span class='line-number'>47</span>
<span class='line-number'>48</span>
<span class='line-number'>49</span>
<span class='line-number'>50</span>
<span class='line-number'>51</span>
<span class='line-number'>52</span>
<span class='line-number'>53</span>
<span class='line-number'>54</span>
<span class='line-number'>55</span>
<span class='line-number'>56</span>
<span class='line-number'>57</span>
<span class='line-number'>58</span>
<span class='line-number'>59</span>
<span class='line-number'>60</span>
<span class='line-number'>61</span>
<span class='line-number'>62</span>
<span class='line-number'>63</span>
<span class='line-number'>64</span>
<span class='line-number'>65</span>
<span class='line-number'>66</span>
<span class='line-number'>67</span>
</pre></td><td class='code'><pre><code class='c'><span class='line'><span class="cp">#define _GNU_SOURCE</span>
</span><span class='line'><span class="cp">#include <sched.h></span>
</span><span class='line'><span class="cp">#include <stdio.h></span>
</span><span class='line'><span class="cp">#include <errno.h></span>
</span><span class='line'><span class="cp">#include <stdlib.h></span>
</span><span class='line'>
</span><span class='line'><span class="c1">// cache line size</span>
</span><span class='line'><span class="c1">// hardware dependent value</span>
</span><span class='line'><span class="c1">// it can checks from /proc/cpuinfo</span>
</span><span class='line'><span class="cp">#define CACHE_LINE_SIZE 64</span>
</span><span class='line'>
</span><span class='line'><span class="c1">// shared data aligned with cache line size</span>
</span><span class='line'><span class="k">struct</span> <span class="n">shared_data</span> <span class="p">{</span>
</span><span class='line'> <span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">__attribute__</span> <span class="p">((</span><span class="n">aligned</span> <span class="p">(</span><span class="n">CACHE_LINE_SIZE</span><span class="p">)))</span> <span class="n">num_proc1</span><span class="p">;</span>
</span><span class='line'> <span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">__attribute__</span> <span class="p">((</span><span class="n">aligned</span> <span class="p">(</span><span class="n">CACHE_LINE_SIZE</span><span class="p">)))</span> <span class="n">num_proc2</span><span class="p">;</span>
</span><span class='line'><span class="p">};</span>
</span><span class='line'>
</span><span class='line'><span class="k">struct</span> <span class="n">shared_data</span> <span class="n">shared</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="c1">// define loops to run for a while</span>
</span><span class='line'><span class="kt">int</span> <span class="n">loop_i</span> <span class="o">=</span> <span class="mi">100000</span><span class="p">,</span> <span class="n">loop_j</span> <span class="o">=</span> <span class="mi">100000</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">child</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'><span class="cp">#define STACK_SIZE (8 * 1024)</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'> <span class="n">pid_t</span> <span class="n">pid</span><span class="p">;</span>
</span><span class='line'> <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* Stack */</span>
</span><span class='line'> <span class="kt">char</span> <span class="o">*</span><span class="n">stack</span> <span class="o">=</span> <span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">malloc</span><span class="p">(</span><span class="n">STACK_SIZE</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">stack</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">perror</span><span class="p">(</span><span class="s">"malloc"</span><span class="p">);</span>
</span><span class='line'> <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">printf</span><span class="p">(</span><span class="s">"main: shared %p %p</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="p">,</span> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* clone a thread sharing memory space with the parent process */</span>
</span><span class='line'> <span class="k">if</span> <span class="p">((</span><span class="n">pid</span> <span class="o">=</span> <span class="n">clone</span><span class="p">(</span><span class="n">child</span><span class="p">,</span> <span class="n">stack</span> <span class="o">+</span> <span class="n">STACK_SIZE</span><span class="p">,</span> <span class="n">CLONE_VM</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">))</span> <span class="o"><</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">perror</span><span class="p">(</span><span class="s">"clone"</span><span class="p">);</span>
</span><span class='line'> <span class="n">exit</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">loop_i</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">for</span><span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o"><</span> <span class="n">loop_j</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="o">++</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="kt">int</span> <span class="nf">child</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="n">arg</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'> <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="n">printf</span><span class="p">(</span><span class="s">"child: shared %p %p</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc1</span><span class="p">,</span> <span class="o">&</span><span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">loop_i</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">for</span> <span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o"><</span> <span class="n">loop_j</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">shared</span><span class="p">.</span><span class="n">num_proc2</span><span class="o">++</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>
<h3>Testing</h3>
<p>I was using the Oprofile 0.99 which has ‘operf’ program that allows non-root users to profile a specified individual process with less setup. Different CPUs have different supported events. The supported events, their meanings and accepted event format by operf can be checked from ophelp and the CPU’s hardware manual. In this experiment, the CLOCK event is CPU_CLK_UNHALTED and L2_LINES_IN is the number of allocated lines in L2 which is L2 cache missing number. As examples, the “CPU_CLK_UNHALTED:100000” tells operf to sample every 100000 unhalted clock with default mask(unhalted core cycles). The “L2_LINES_IN:100000:0xf0” tells operf to sample every 1000000 number of allocated lines in L2 on all cores with all prefetch inclusive.</p>
<p>The following is the experiment results.</p>
<figure class='code'><figcaption><span>profiling result of alignment</span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$time</span> operf --event<span class="o">=</span>CPU_CLK_UNHALTED:100000,L2_LINES_IN:100000:0xf0 ./alignment
</span><span class='line'>
</span><span class='line'>operf: Profiler started
</span><span class='line'>main: shared 0x6010c0 0x601100
</span><span class='line'>child: shared 0x6010c0 0x601100
</span><span class='line'>
</span><span class='line'>profiled app exited with the following status: 160
</span><span class='line'>
</span><span class='line'>Profiling <span class="k">done</span>.
</span><span class='line'>
</span><span class='line'>real 0m41.373s
</span><span class='line'>user 0m54.015s
</span><span class='line'>sys 0m0.728s
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="nv">$opreport</span>
</span><span class='line'>Using /home/work/oprof_cache/oprofile_data/samples/ <span class="k">for </span>samples directory.
</span><span class='line'>CPU: Core 2, speed 2.401e+06 MHz <span class="o">(</span>estimated<span class="o">)</span>
</span><span class='line'>Counted CPU_CLK_UNHALTED events <span class="o">(</span>Clock cycles when not halted<span class="o">)</span> with a unit mask of 0x00 <span class="o">(</span>Unhalted core cycles<span class="o">)</span> count 100000
</span><span class='line'>Counted L2_LINES_IN events <span class="o">(</span>number of allocated lines in L2<span class="o">)</span> with a unit mask of 0xf0 <span class="o">(</span>multiple flags<span class="o">)</span> count 100000
</span><span class='line'>CPU_CLK_UNHALT...|L2_LINES_IN:10...|
</span><span class='line'> samples| %| samples| %|
</span><span class='line'>------------------------------------
</span><span class='line'> 939093 100.000 396933 100.000 alignment
</span><span class='line'> CPU_CLK_UNHALT...|L2_LINES_IN:10...|
</span><span class='line'> samples| %| samples| %|
</span><span class='line'> ------------------------------------
</span><span class='line'> 936430 99.7164 395920 99.7448 alignment
</span><span class='line'> 2657 0.2829 1013 0.2552 no-vmlinux
</span><span class='line'> 5 5.3e-04 0 0 ld-2.15.so
</span><span class='line'> 1 1.1e-04 0 0 libc-2.15.so
</span></code></pre></td></tr></table></div></figure>
<figure class='code'><figcaption><span>profiling result of no_alignment</span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$time</span> operf --event<span class="o">=</span>CPU_CLK_UNHALTED:100000,L2_LINES_IN:100000:0xf0 ./no_alignment
</span><span class='line'>operf: Profiler started
</span><span class='line'>main: shared 0x601058 0x60105c
</span><span class='line'>child: shared 0x601058 0x60105c
</span><span class='line'>profiled app exited with the following status: 160
</span><span class='line'>
</span><span class='line'>Profiling <span class="k">done</span>.
</span><span class='line'>
</span><span class='line'>real 1m24.739s
</span><span class='line'>user 1m59.167s
</span><span class='line'>sys 0m1.344s
</span><span class='line'>
</span><span class='line'><span class="nv">$opreport</span>
</span><span class='line'>Using /home/work/oprof_cache/oprofile_data/samples/ <span class="k">for </span>samples directory.
</span><span class='line'>CPU: Core 2, speed 2.401e+06 MHz <span class="o">(</span>estimated<span class="o">)</span>
</span><span class='line'>Counted CPU_CLK_UNHALTED events <span class="o">(</span>Clock cycles when not halted<span class="o">)</span> with a unit mask of 0x00 <span class="o">(</span>Unhalted core cycles<span class="o">)</span> count 100000
</span><span class='line'>Counted L2_LINES_IN events <span class="o">(</span>number of allocated lines in L2<span class="o">)</span> with a unit mask of 0xf0 <span class="o">(</span>multiple flags<span class="o">)</span> count 100000
</span><span class='line'>CPU_CLK_UNHALT...|L2_LINES_IN:10...|
</span><span class='line'> samples| %| samples| %|
</span><span class='line'>------------------------------------
</span><span class='line'> 1423030 100.000 1177262 100.000 no_alignment
</span><span class='line'> CPU_CLK_UNHALT...|L2_LINES_IN:10...|
</span><span class='line'> samples| %| samples| %|
</span><span class='line'> ------------------------------------
</span><span class='line'> 1419249 99.7343 1174038 99.7261 no_alignment
</span><span class='line'> 3778 0.2655 3224 0.2739 no-vmlinux
</span><span class='line'> 2 1.4e-04 0 0 ld-2.15.so
</span><span class='line'> 1 7.0e-05 0 0 libc-2.15.so
</span></code></pre></td></tr></table></div></figure>
<h3>Analysis and Conclusion</h3>
<p>I drawed the table for the analysising.</p>
<p><img src="media/Oprofile-and-Cache/Oprofile-and-Cache.png"></p>
<p>Here is the conclusion:</p>
<ul>
<li>The cache missing rate of no_alignment was 82.73%. It became 42.27% with alignment optimization. The cache missing rate was reduced to almost half.</li>
<li>The no_alignment ran 120.5 seconds and the alignment ran 55 seconds. It was a bit more than double faster with alignment optimization.</li>
</ul>
<blockquote><p><strong>NOTE:</strong> The real time is less than user + sys because the program runs on mutlecores parallel</p></blockquote>
</div>
</article>
<article>
<header class="page-header">
<h1 class="entry-title"><a href="/blog/2014/03/09/a-piece-of-code-refactoring/">一段代码的重构</a></h1>
<p class="meta">
<time datetime="2014-03-09T16:26:03-07:00" pubdate data-updated="true">Mar 9<span>th</span>, 2014</time>
</p>
</header>
<div class="entry-content"><h3>为什么要对这段代码重构</h3>
<p>上周对一段代码进行了重构，这段代码是参加一个小组的code review时读到的，这段代码并不长，只有100多行，我花了几个小时（也许两个小时），但是没有读明白这段代码是如何工作的。因为代码可读性不好，代码阅读者的时间就这样被浪费了而没有任何收获。而且代码的书写者在一段时间后也会面临同样的问题，他／她至少需要一点时间才能明白代码如何工作的。还有很重要的一点是，从长远来看，这样的代码可维护性也不高，引入新的改动会比较难或者比较容易引入新的bug。为了避免下一个代码阅读者掉入同样的一个“坑”，我提出需要对代码重构。</p>
<h3>为什么可读性不高</h3>
<p>原始代码请看后面，它的可读性不好主要体现在以下几点：</p>
<ul>
<li>变量的命名可读性。比如dummy命名为isdummy，peek_dummy命名为next_msg_isdummy的可读性会更好，sleep_entry实际上就是!q->msg_queue_pending_msgs变量有重复之嫌。关于如何命名可以参考<a href="http://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882/ref=sr_1_1?ie=UTF8&qid=1394416932&sr=8-1&keywords=clean+code" title="Clean Code: A Handbook of Agile Software Craftsmanship">clean code</a>。</li>
<li>do … while的循环条件是一个长条件(((*head == NULL) && !sleep_entry) || (dummy && sleep_entry) || unlikely(peek_dummy))，难读懂，这是造成可读性不好的主要原因，其实际体现出来的是代码的逻辑（或者流程）不清晰</li>
<li>函数的长度很长。并不是说长函数的可读性一定有问题，但是长函数往往是有问题，它通常反映代码书写者对代码没有进行很好的抽象。抽象是书写代码最终要的一种能力，如果我们打开备受<a href="http://norvig.com/" title="Peter Norvig">Peter Norvig</a>推崇的<a href="http://mitpress.mit.edu/sicp/full-text/book/book.html" title="Structure and Interpretation of Computer Programs">Structure and Interpretation of Computer Programs</a>一书，它的第一章就是Building Abstractions with Procedures</li>
<li>注释太少，一些需要注释的而没有，例如上面提到的do … while循环的三个条件</li>
</ul>
<p>通过与拥有这段代码的小组讨论之后，代码的意图实际上如下面的流程图所示：</p>
<p><img src="media/a-piece-of-code-refactoring/flowchart.png"></p>
<p>流程图没有经过简化，有一部分模块是重复的，但是可以让我们理解原代码的意图是什么。可以看到原代码将整个流程都在一个do … while中实现了，这就导致代码结构不清晰。</p>
<h3>代码重构中遵循的一些原则</h3>
<p>重构后的代码请看后面，那么重构中遵循了哪些原则呢？并不复杂，只要写代码过程中，留意下面几条原则，代码的可读性就可以得到极大的提高。</p>
<ul>
<li>给变量和函数一个可读性好的名字，正如我们在clean code中学到的</li>
<li>给if, when, switch等中的逻辑条件（condition）一个体现意图的可读性强的名字，这个condition可以是变量判断或者函数返回值实现的。</li>
<li>保持函数在一个合理的长度</li>
<li>在必要的时候画流程图可以解决混乱，注意这里流程图画的是我们希望代码做什么，而不是我们已经写的代码的流程图，这点很重要，因为我们要写出是执行我们意图的代码</li>
<li>DRY principle，即不要在不同的代码重复相同的代码和信息</li>
<li>就象写完文章之前最后再把文章读一边，在提交代码前把代码再读一边，通常我们都可以发现一些改进的点。不要担心这会导致无止无=尽的修改，最终我们会到达一个我们能接受的点，另外deadline也会迫使我们在适当的时候停下。</li>
</ul>
<h3>重构之后的一些反思</h3>
<ul>
<li>我始终认为代码的可读性是最重要的，尤其是现在代码的开发都是团队合作的结果。虽然重构后的代码有将近200多行，这是因为有更多的函数，注释和空格。但新的代码可读性更好，长远看更容易维护（意味着成本更低）</li>
<li>写可读性强的代码需要时间，所以在计划和估计任务时请考虑这点</li>
<li>可读性好的代码不是一蹴而就的，好的代码通常是通过反复的、慢慢的改进而来，我想这就是为什么需要经常性的代码重构的思想的来源</li>
<li>可读性好的代码让读代码的人获得乐趣，写代码的人也会因为写了一份好的代码而获得乐趣</li>
<li>也许一开始我们写可读性好的代码会有难度或者觉得花费时间，但是只要坚持上述提到的原则，早晚我们可以又快又好的写出漂亮的代码</li>
<li>保持stupid simple，就象功夫，花巧并不一定好，真正的高手只用基础招数的组合</li>
<li>没有UT也可以重构，也不影响写出一个好的代码，但是看下一条</li>
<li>当代码提交后，新代码review之后，碰到的一个问题是：是否应该将新代码提交，这样的犹豫是因为没有足够的UT和funtional测试。完全可以理解，所以这就是为什么需要UT和CI。当然我这里也有个疑惑就是Linux Kernel开发没有UT，那么在Linuxe Kernel的演化过程中，它的开发人员是如何获得这样的信心的</li>
</ul>
<h3>重构前的代码</h3>
<figure class='code'><figcaption><span>[原始代码] (recv_whole_msg_origin.c)</span> <a href='/downloads/code/a-piece-of-code-refactoring/recv_whole_msg_origin.c'>download</a></figcaption>
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</pre></td><td class='code'><pre><code class='c'><span class='line'><span class="kt">int</span> <span class="nf">msg_recv_whole_msg</span><span class="p">(</span><span class="k">struct</span> <span class="n">msg_client</span> <span class="o">*</span><span class="n">client</span><span class="p">,</span> <span class="k">struct</span> <span class="n">msg_frag</span> <span class="o">**</span><span class="n">head</span><span class="p">,</span> <span class="kt">int</span> <span class="n">nonblock</span><span class="p">,</span>
</span><span class='line'> <span class="k">struct</span> <span class="n">timespec</span> <span class="o">*</span><span class="n">ts</span><span class="p">)</span>
</span><span class='line'><span class="p">{</span>
</span><span class='line'> <span class="k">struct</span> <span class="n">msg_frag</span> <span class="o">*</span><span class="n">cur_msg</span><span class="p">;</span>
</span><span class='line'> <span class="k">struct</span> <span class="n">msg_queue</span> <span class="o">*</span><span class="n">q</span><span class="p">;</span>
</span><span class='line'> <span class="k">struct</span> <span class="n">ext_wait_queue</span> <span class="n">wait</span><span class="p">;</span>
</span><span class='line'> <span class="k">struct</span> <span class="n">timeval</span> <span class="n">tv</span><span class="p">;</span>
</span><span class='line'> <span class="kt">int</span> <span class="n">ret</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
</span><span class='line'> <span class="kt">long</span> <span class="n">timeout</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
</span><span class='line'> <span class="n">bool</span> <span class="n">dummy</span><span class="p">,</span> <span class="n">peek_dummy</span><span class="p">,</span> <span class="n">sleep_entry</span><span class="p">;</span>
</span><span class='line'> <span class="n">bool</span> <span class="n">first_entry</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
</span><span class='line'> <span class="n">buffer_bottom_t</span><span class="o">*</span> <span class="n">bb</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
</span><span class='line'> <span class="o">*</span><span class="n">head</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="n">g_enable_timestamps</span><span class="p">)</span>
</span><span class='line'> <span class="n">do_gettimeofday</span><span class="p">(</span><span class="o">&</span><span class="n">tv</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="n">rcu_read_lock</span><span class="p">();</span> <span class="c1">// make sure q is not freed (in RCU call back)</span>
</span><span class='line'> <span class="n">q</span> <span class="o">=</span> <span class="n">client</span><span class="o">-></span><span class="n">q</span><span class="p">;</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">unlikely</span><span class="p">(</span><span class="o">!</span><span class="n">q</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">rcu_read_unlock</span><span class="p">();</span>
</span><span class='line'> <span class="k">return</span> <span class="o">-</span><span class="n">ENOTCONN</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">prefetch</span><span class="p">(</span><span class="n">q</span><span class="p">);</span>
</span><span class='line'> <span class="n">timeout</span> <span class="o">=</span> <span class="n">__prepare_timeout</span><span class="p">(</span><span class="n">ts</span><span class="p">);</span>
</span><span class='line'> <span class="k">do</span> <span class="p">{</span>
</span><span class='line'> <span class="n">spin_lock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="n">likely</span><span class="p">(</span><span class="n">first_entry</span><span class="p">)){</span>
</span><span class='line'> <span class="n">rcu_read_unlock</span><span class="p">();</span> <span class="c1">//we can unlock RCU because spin_lock_bh already disabled preempt</span>
</span><span class='line'> <span class="n">first_entry</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'> <span class="cm">/* Make sure next message is dummy because other threads may fetch it. */</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">__next_msg_is_dummy</span><span class="p">(</span><span class="n">q</span><span class="p">)</span> <span class="o">&&</span> <span class="p">((</span><span class="o">*</span><span class="n">head</span><span class="p">)</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">spin_unlock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="k">break</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">q</span><span class="o">-></span><span class="n">msg_queue_pending_msgs</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">sleep_entry</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
</span><span class='line'> <span class="n">DTRACE</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="s">"msg_recv_whole_msg(): Msg priority queue not empty.</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="n">cur_msg</span> <span class="o">=</span> <span class="n">__get_first_msg</span><span class="p">(</span><span class="n">q</span><span class="p">,</span> <span class="nb">false</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">unlikely</span><span class="p">(</span><span class="n">cur_msg</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">spin_unlock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="n">EPRINTF</span><span class="p">(</span><span class="s">"Msg Q list empty while counter for msg is %u</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="n">q</span><span class="o">-></span><span class="n">msg_queue_pending_msgs</span><span class="p">);</span>
</span><span class='line'> <span class="k">return</span> <span class="o">-</span><span class="n">ERANGE</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="n">dummy</span> <span class="o">=</span> <span class="n">MSG_IS_DUMMY_MSG</span><span class="p">(</span><span class="n">MSGHEADER</span><span class="p">(</span><span class="n">cur_msg</span><span class="p">));</span>
</span><span class='line'>
</span><span class='line'> <span class="n">bb</span> <span class="o">=</span> <span class="p">(</span><span class="n">buffer_bottom_t</span> <span class="o">*</span><span class="p">)(</span><span class="n">cur_msg</span><span class="o">-></span><span class="n">data</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="n">q</span><span class="o">-></span><span class="n">msg_queue_pending_msgs</span><span class="o">--</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">dummy</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">q</span><span class="o">-></span><span class="n">msg_queue_pending_dummy_msgs</span><span class="o">--</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">need_input_sync</span><span class="p">(</span><span class="n">client</span><span class="p">,</span> <span class="n">cur_msg</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">client</span><span class="o">-></span><span class="n">q</span><span class="o">-></span><span class="n">msg_queue_pending_wosp_msgs</span><span class="o">--</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">MSG_IS_SYNC_MSG</span><span class="p">(</span><span class="n">bb</span><span class="p">)){</span>
</span><span class='line'> <span class="n">q</span><span class="o">-></span><span class="n">msg_queue_size</span> <span class="o">-=</span> <span class="n">cur_msg</span><span class="o">-></span><span class="n">n_bufs</span><span class="p">;</span>
</span><span class='line'> <span class="n">q</span><span class="o">-></span><span class="n">msg_queue_msgs</span><span class="o">--</span><span class="p">;</span>
</span><span class='line'> <span class="n">msg_pid_queue_stat_dec</span><span class="p">(</span><span class="n">q</span><span class="p">,</span> <span class="n">bb</span><span class="o">-></span><span class="n">process_id</span><span class="p">,</span> <span class="n">cur_msg</span><span class="o">-></span><span class="n">n_bufs</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">recv_input_sync_prepare</span><span class="p">(</span><span class="n">client</span><span class="p">,</span> <span class="n">cur_msg</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// must put behind sync msg send out, for sync msg will use filler2.</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">dummy</span><span class="p">){</span>
</span><span class='line'> <span class="n">bb</span><span class="o">-></span><span class="n">filler2</span> <span class="o">=</span> <span class="p">(</span><span class="n">bb</span><span class="o">-></span><span class="n">filler2</span> <span class="o">&</span> <span class="mh">0xffff0000</span><span class="p">)</span><span class="o">|</span> <span class="n">get_and_inc_hand_seq</span><span class="p">(</span><span class="n">q</span><span class="p">,</span> <span class="n">bb</span><span class="o">-></span><span class="n">process_id</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* Take a peek whether the next message is a dummy message. */</span>
</span><span class='line'> <span class="n">peek_dummy</span> <span class="o">=</span> <span class="n">__next_msg_is_dummy</span><span class="p">(</span><span class="n">q</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="n">spin_unlock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="n">recv_input_sync</span><span class="p">(</span><span class="n">client</span><span class="p">,</span> <span class="n">cur_msg</span><span class="p">);</span>
</span><span class='line'> <span class="n">ret</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'> <span class="n">cur_msg</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
</span><span class='line'> <span class="n">dummy</span> <span class="o">=</span> <span class="n">peek_dummy</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
</span><span class='line'> <span class="n">sleep_entry</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">unlikely</span><span class="p">(</span><span class="n">nonblock</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">DPRINTF</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="s">"msg_recv_whole_msg(): nonblock, don't sleep</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
</span><span class='line'> <span class="n">spin_unlock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="n">ret</span> <span class="o">=</span> <span class="o">-</span><span class="n">EAGAIN</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="n">unlikely</span><span class="p">(</span><span class="n">timeout</span> <span class="o"><</span> <span class="mi">0</span><span class="p">))</span> <span class="p">{</span>
</span><span class='line'> <span class="n">DPRINTF</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="s">"msg_recv_whole_msg(): timeout < 0: %ld</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">timeout</span><span class="p">);</span>
</span><span class='line'> <span class="n">spin_unlock_bh</span><span class="p">(</span><span class="o">&</span><span class="n">q</span><span class="o">-></span><span class="n">lock</span><span class="p">);</span>
</span><span class='line'> <span class="n">ret</span> <span class="o">=</span> <span class="o">-</span><span class="n">ETIMEDOUT</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">else</span> <span class="p">{</span>
</span><span class='line'> <span class="n">wait</span><span class="p">.</span><span class="n">task</span> <span class="o">=</span> <span class="n">current</span><span class="p">;</span>
</span><span class='line'> <span class="n">wait</span><span class="p">.</span><span class="n">state</span> <span class="o">=</span> <span class="n">STATE_NONE</span><span class="p">;</span>
</span><span class='line'> <span class="n">DPRINTF</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="s">"msg_recv_whole_msg(): going to sleep.</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
</span><span class='line'> <span class="n">ret</span> <span class="o">=</span> <span class="n">__wq_sleep</span><span class="p">(</span><span class="o">&</span><span class="n">client</span><span class="o">-></span><span class="n">q</span><span class="p">,</span> <span class="o">&</span><span class="n">timeout</span><span class="p">,</span> <span class="o">&</span><span class="n">wait</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">ret</span> <span class="o">==</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">cur_msg</span> <span class="o">=</span> <span class="n">wait</span><span class="p">.</span><span class="n">head</span><span class="p">;</span>
</span><span class='line'> <span class="n">recv_input_sync</span><span class="p">(</span><span class="n">client</span><span class="p">,</span> <span class="n">cur_msg</span><span class="p">);</span>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="n">unlikely</span><span class="p">(</span><span class="n">MSG_IS_DUMMY_MSG</span><span class="p">(</span><span class="n">MSGHEADER</span><span class="p">(</span><span class="n">cur_msg</span><span class="p">)))){</span>
</span><span class='line'> <span class="n">WPRINTF</span><span class="p">(</span><span class="s">"Unexpected dummy message received in wait task. From %x.%x.</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
</span><span class='line'> <span class="n">MSGHEADER</span><span class="p">(</span><span class="n">cur_msg</span><span class="p">)</span><span class="o">-></span><span class="n">computer</span><span class="p">,</span><span class="n">MSGHEADER</span><span class="p">(</span><span class="n">cur_msg</span><span class="p">)</span><span class="o">-></span><span class="n">family</span><span class="p">);</span>
</span><span class='line'> <span class="n">dummy</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="n">DTRACE</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="s">"msg_recv_whole_msg() ret: %d, msg:(%p)</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">ret</span><span class="p">,</span> <span class="n">cur_msg</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="n">dummy</span><span class="p">)</span>
</span><span class='line'> <span class="n">msg_free_msg</span><span class="p">(</span><span class="o">&</span><span class="n">cur_msg</span><span class="p">);</span>
</span><span class='line'> <span class="k">else</span> <span class="k">if</span> <span class="p">((</span><span class="o">*</span><span class="n">head</span><span class="p">)</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="c1">//Store the non-dummy message to receiver</span>
</span><span class='line'> <span class="o">*</span><span class="n">head</span> <span class="o">=</span> <span class="n">cur_msg</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span> <span class="k">while</span> <span class="p">(((</span><span class="o">*</span><span class="n">head</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="o">&&</span> <span class="o">!</span><span class="n">sleep_entry</span><span class="p">)</span> <span class="o">||</span> <span class="p">(</span><span class="n">dummy</span> <span class="o">&&</span> <span class="n">sleep_entry</span><span class="p">)</span> <span class="o">||</span> <span class="n">unlikely</span><span class="p">(</span><span class="n">peek_dummy</span><span class="p">));</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/* restore bb->phys_computer because all input-sync related logic is completed here</span>
</span><span class='line'><span class="cm"> restore it so that monitor tools sees compliant data as cIPA */</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="o">*</span><span class="n">head</span><span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="n">bb</span> <span class="o">=</span> <span class="p">(</span><span class="n">buffer_bottom_t</span> <span class="o">*</span><span class="p">)(</span><span class="o">*</span><span class="n">head</span><span class="p">)</span><span class="o">-></span><span class="n">data</span><span class="p">;</span>
</span><span class='line'> <span class="n">bb</span><span class="o">-></span><span class="n">phys_computer</span> <span class="o">=</span> <span class="n">bb</span><span class="o">-></span><span class="n">next_phys_computer</span><span class="p">;</span>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="n">g_enable_timestamps</span><span class="p">){</span>
</span><span class='line'> <span class="n">set_time_rec</span><span class="p">(</span><span class="o">*</span><span class="n">head</span><span class="p">,</span> <span class="n">TIMEREC_ENTER_IOCTL</span><span class="p">,</span> <span class="o">&</span><span class="n">tv</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="n">__msg_monitor</span><span class="p">(</span><span class="o">*</span><span class="n">head</span><span class="p">,</span> <span class="n">MON_POINTS_T_RECEIVE_C</span><span class="p">);</span>