<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/75677>75677</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [OpenMP] Performance degradation from devices reorganization
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            openmp,
            openmp:libomptarget
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            jdoerfert
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          dhruvachak
      </td>
    </tr>
</table>

<pre>
    @ronlieb collected some performance numbers using versions of the upstream compiler that show degradations after the devices reorganization. It appears that https://github.com/llvm/llvm-project/pull/74397 is one of the patches causing the degradation. Currently, all available devices on a system are being initialized eagerly. Previously, only devices that were being used by an application would be initialized.

These are the llvm-project before/after commits used for comparison.

Before SHA: bb0f162b
After SHA: 77c40ea3

SPEChpc 2021 benchmark 505.lbm degraded 10% when using 8 MPI ranks on a system with 8 AMD GPUs. The configuration tested is the default setting without the env-var ROCR_VISIBLE_DEVICES set.
</pre>
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