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<a href="#pub-methods">Public Member Functions</a> &#124;
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<p>Lightweight spinlock.
<a href="classimpala_1_1SpinLock.html#details">More...</a></p>
<p><code>#include &lt;<a class="el" href="spinlock_8h_source.html">spinlock.h</a>&gt;</code></p>
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Collaboration diagram for impala::SpinLock:</div>
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Public Member Functions</h2></td></tr>
<tr class="memitem:afa0ac276aacd3f7d77c7b50b2428c22b"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#afa0ac276aacd3f7d77c7b50b2428c22b">SpinLock</a> ()</td></tr>
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<tr class="memitem:ad65f0b82396ed5c56cd62cddd337569a"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#ad65f0b82396ed5c56cd62cddd337569a">lock</a> ()</td></tr>
<tr class="memdesc:ad65f0b82396ed5c56cd62cddd337569a"><td class="mdescLeft">&#160;</td><td class="mdescRight">Acquires the lock, spins until the lock becomes available. <a href="#ad65f0b82396ed5c56cd62cddd337569a">More...</a><br/></td></tr>
<tr class="separator:ad65f0b82396ed5c56cd62cddd337569a"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a009af2b04936652a3ae3969452943ad5"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#a009af2b04936652a3ae3969452943ad5">unlock</a> ()</td></tr>
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<tr class="memitem:a364661c605091ab15a00e505cbfac67c"><td class="memItemLeft" align="right" valign="top"><a class="el" href="classbool.html">bool</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#a364661c605091ab15a00e505cbfac67c">try_lock</a> ()</td></tr>
<tr class="memdesc:a364661c605091ab15a00e505cbfac67c"><td class="mdescLeft">&#160;</td><td class="mdescRight">Tries to acquire the lock. <a href="#a364661c605091ab15a00e505cbfac67c">More...</a><br/></td></tr>
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<tr class="memitem:ace3db57e5ecd6110b31cd59a21fdeb95"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#ace3db57e5ecd6110b31cd59a21fdeb95">DCheckLocked</a> ()</td></tr>
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Private Member Functions</h2></td></tr>
<tr class="memitem:a1a55557709a3a25c85f14959a30d2990"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#a1a55557709a3a25c85f14959a30d2990">SlowAcquire</a> ()</td></tr>
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Private Attributes</h2></td></tr>
<tr class="memitem:a1c02b8529e317aa7c0ea821efb154ea9"><td class="memItemLeft" align="right" valign="top"><a class="el" href="classbool.html">bool</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#a1c02b8529e317aa7c0ea821efb154ea9">locked_</a></td></tr>
<tr class="memdesc:a1c02b8529e317aa7c0ea821efb154ea9"><td class="mdescLeft">&#160;</td><td class="mdescRight">TODO: pad this to be a cache line? <a href="#a1c02b8529e317aa7c0ea821efb154ea9">More...</a><br/></td></tr>
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<tr class="memitem:af55a180118b1af36d6f5a2ad37aedef8"><td class="memItemLeft" align="right" valign="top">static const int&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classimpala_1_1SpinLock.html#af55a180118b1af36d6f5a2ad37aedef8">NUM_SPIN_CYCLES</a> = 70</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Lightweight spinlock. </p>
<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00024">24</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<td class="memname">impala::SpinLock::SpinLock </td>
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<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00026">26</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<h2 class="groupheader">Member Function Documentation</h2>
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<td class="memname">void impala::SpinLock::DCheckLocked </td>
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<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00043">43</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>References <a class="el" href="spinlock_8h_source.html#l00067">locked_</a>.</p>
<p>Referenced by <a class="el" href="coordinator_8h_source.html#l00173">impala::exec_summary()</a>.</p>
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<p>Acquires the lock, spins until the lock becomes available. </p>
<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00029">29</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>References <a class="el" href="spinlock_8cc_source.html#l00018">SlowAcquire()</a>, and <a class="el" href="spinlock_8h_source.html#l00041">try_lock()</a>.</p>
<p>Referenced by <a class="el" href="streaming-sampler_8h_source.html#l00088">impala::StreamingSampler&lt; int64_t, 64 &gt;::GetSamples()</a>.</p>
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<p>Out-of-line definition of the actual spin loop. The primary goal is to have the actual lock method as short as possible to avoid polluting the i-cache with unnecessary instructions in the non-contested case. </p>
<p>Definition at line <a class="el" href="spinlock_8cc_source.html#l00018">18</a> of file <a class="el" href="spinlock_8cc_source.html">spinlock.cc</a>.</p>
<p>References <a class="el" href="atomic_8h_source.html#l00032">impala::AtomicUtil::CpuWait()</a>, <a class="el" href="spinlock_8h_source.html#l00065">NUM_SPIN_CYCLES</a>, and <a class="el" href="spinlock_8h_source.html#l00041">try_lock()</a>.</p>
<p>Referenced by <a class="el" href="spinlock_8h_source.html#l00029">lock()</a>.</p>
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<p>Tries to acquire the lock. </p>
<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00041">41</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>References <a class="el" href="spinlock_8h_source.html#l00067">locked_</a>.</p>
<p>Referenced by <a class="el" href="spinlock_8h_source.html#l00029">lock()</a>, and <a class="el" href="spinlock_8cc_source.html#l00018">SlowAcquire()</a>.</p>
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<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00033">33</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>References <a class="el" href="spinlock_8h_source.html#l00067">locked_</a>.</p>
<p>Referenced by <a class="el" href="runtime-profile_8cc_source.html#l00507">impala::RuntimeProfile::PrettyPrint()</a>, and <a class="el" href="runtime-profile_8cc_source.html#l00868">impala::RuntimeProfile::TimeSeriesCounter::ToThrift()</a>.</p>
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<h2 class="groupheader">Member Data Documentation</h2>
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<td class="memname"><a class="el" href="classbool.html">bool</a> impala::SpinLock::locked_</td>
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<p>TODO: pad this to be a cache line? </p>
<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00067">67</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>Referenced by <a class="el" href="spinlock_8h_source.html#l00043">DCheckLocked()</a>, <a class="el" href="spinlock_8h_source.html#l00041">try_lock()</a>, and <a class="el" href="spinlock_8h_source.html#l00033">unlock()</a>.</p>
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<td class="memname">const int impala::SpinLock::NUM_SPIN_CYCLES = 70</td>
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<p>In typical spin lock implements, we want to spin (and keep the core fully busy), for some number of cycles before yielding. Consider these three cases: 1) lock is un-contended - spinning doesn't kick in and has no effect. 2) lock is taken by another thread and that thread finishes quickly. 3) lock is taken by another thread and that thread is slow (e.g. scheduled away).</p>
<p>In case 3), we'd want to yield so another thread can do work. This thread won't be able to do anything useful until the thread with the lock runs again. In case 2), we don't want to yield (and give up our scheduling time slice) since we will get to run soon after. To try to get the best of everything, we will busy spin for a while before yielding to another thread. TODO: how do we set this. </p>
<p>Definition at line <a class="el" href="spinlock_8h_source.html#l00065">65</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
<p>Referenced by <a class="el" href="spinlock_8cc_source.html#l00018">SlowAcquire()</a>.</p>
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<hr/>The documentation for this class was generated from the following files:<ul>
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<li>be/src/util/<a class="el" href="spinlock_8cc_source.html">spinlock.cc</a></li>
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