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     <h4 class="title">
      <a name="performance-schema-performance-timers-table">
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      29.12.22.6 The performance_timers Table
     </h4>
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  <a class="indexterm" name="idm46045067404608">
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  <p>
   The
   <a class="link" href="performance-schema-performance-timers-table.html" title="29.12.22.6 The performance_timers Table">
    <code class="literal">
     performance_timers
    </code>
   </a>
   table
          shows which event timers are available:
  </p>
  <div class="copytoclipboard-wrapper">
   <pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34080340"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql&gt;</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>performance_timers<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> TIMER_NAME  <span class="token punctuation">|</span> TIMER_FREQUENCY <span class="token punctuation">|</span> TIMER_RESOLUTION <span class="token punctuation">|</span> TIMER_OVERHEAD <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CYCLE       <span class="token punctuation">|</span>      2389029850 <span class="token punctuation">|</span>                1 <span class="token punctuation">|</span>             72 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NANOSECOND  <span class="token punctuation">|</span>      1000000000 <span class="token punctuation">|</span>                1 <span class="token punctuation">|</span>            112 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> MICROSECOND <span class="token punctuation">|</span>         1000000 <span class="token punctuation">|</span>                1 <span class="token punctuation">|</span>            136 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> MILLISECOND <span class="token punctuation">|</span>            1036 <span class="token punctuation">|</span>                1 <span class="token punctuation">|</span>            168 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> THREAD_CPU  <span class="token punctuation">|</span>       339101694 <span class="token punctuation">|</span>                1 <span class="token punctuation">|</span>            798 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
  </div>
  <p>
   If the values associated with a given timer name are
   <code class="literal">
    NULL
   </code>
   , that timer is not supported on your
          platform. For an explanation of how event timing occurs, see
   <a class="xref" href="performance-schema-timing.html" title="29.4.1 Performance Schema Event Timing">
    Section 29.4.1, “Performance Schema Event Timing”
   </a>
   .
  </p>
  <p>
   The
   <a class="link" href="performance-schema-performance-timers-table.html" title="29.12.22.6 The performance_timers Table">
    <code class="literal">
     performance_timers
    </code>
   </a>
   table has
          these columns:
  </p>
  <div class="itemizedlist">
   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      <code class="literal">
       TIMER_NAME
      </code>
     </p>
     <p>
      The timer name.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       TIMER_FREQUENCY
      </code>
     </p>
     <p>
      The number of timer units per second. For a cycle timer,
              the frequency is generally related to the CPU speed. For
              example, on a system with a 2.4GHz processor, the
      <code class="literal">
       CYCLE
      </code>
      may be close to 2400000000.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       TIMER_RESOLUTION
      </code>
     </p>
     <p>
      Indicates the number of timer units by which timer values
              increase. If a timer has a resolution of 10, its value
              increases by 10 each time.
     </p>
    </li>
    <li class="listitem">
     <p>
      <code class="literal">
       TIMER_OVERHEAD
      </code>
     </p>
     <p>
      The minimal number of cycles of overhead to obtain one
              timing with the given timer. The Performance Schema
              determines this value by invoking the timer 20 times
              during initialization and picking the smallest value. The
              total overhead really is twice this amount because the
              instrumentation invokes the timer at the start and end of
              each event. The timer code is called only for timed
              events, so this overhead does not apply for nontimed
              events.
     </p>
    </li>
   </ul>
  </div>
  <p>
   The
   <a class="link" href="performance-schema-performance-timers-table.html" title="29.12.22.6 The performance_timers Table">
    <code class="literal">
     performance_timers
    </code>
   </a>
   table has
          no indexes.
  </p>
  <p>
   <a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
    <code class="literal">
     TRUNCATE TABLE
    </code>
   </a>
   is not permitted
          for the
   <a class="link" href="performance-schema-performance-timers-table.html" title="29.12.22.6 The performance_timers Table">
    <code class="literal">
     performance_timers
    </code>
   </a>
   table.
  </p>
 </div>
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