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<th>Priority</th>
<td>medium
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<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - INTEL_DEBUG=shader_time is full of lies"
href="https://bugs.freedesktop.org/show_bug.cgi?id=79029">79029</a>
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<th>Assignee</th>
<td>idr@freedesktop.org
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<th>Summary</th>
<td>INTEL_DEBUG=shader_time is full of lies
</td>
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<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<th>OS</th>
<td>All
</td>
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<th>Reporter</th>
<td>kenneth@whitecape.org
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<th>Hardware</th>
<td>Other
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Version</th>
<td>git
</td>
</tr>
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<th>Component</th>
<td>Drivers/DRI/i965
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<th>Product</th>
<td>Mesa
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<p>
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<pre>INTEL_DEBUG=shader_time reports that almost 0 time is spent in the vertex
shader in a microbenchmark (OglTerrainFlyInst). However, the FS is really
simple, and the VS is pretty large. I managed to cut roughly 50% of the VS
instructions, and that roughly doubled the performance. So clearly the VS is
important.
Using performance monitoring, it looks like the VS actually takes up ~70% of
the time. So, shader_time is just full of lies. It appears that it's
undercounting the VS time in Unigine Valley as well.
I believe the timestamp register is getting reset in almost every VS, so we
just count 0 most of the time.
Perhaps it can be improved? Perhaps we need to develop something better?</pre>
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