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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - 50% perf drop in SynMark Fill* tests (E2E RBC gets disabled?)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=107223">107223</a>
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<th>Summary</th>
<td>50% perf drop in SynMark Fill* tests (E2E RBC gets disabled?)
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<th>Product</th>
<td>Mesa
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<th>Version</th>
<td>git
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
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<th>Component</th>
<td>Drivers/DRI/i965
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<th>Assignee</th>
<td>jason@jlekstrand.net
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<th>Reporter</th>
<td>eero.t.tamminen@intel.com
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<th>QA Contact</th>
<td>intel-3d-bugs@lists.freedesktop.org
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<pre>Setup:
* Ubuntu 16.04
* kernel & X server built from Git
* Modifiers support enabled (requires git version , or latest X release, which
isn't yet in distros)
There's a large performance drop visible in many onscreen tests when using
graphics stack supporting modifiers.
Performance drops on all GEN9+ platforms. Drop is largest in SynMark Fill*
tests on eDRAM machines where the drop is 50%. On GT2 machines they drop ~30%
and on BXT 20%. This drop is visible both with Unity desktop and when using
just plain X server.
Smaller performance drop is visible in most of the other SynMark tests.
I bisected the regression to following commit:
-------------------------------------------------
commit a26693493570a9d0f0fba1be617e01ee7bfff4db
Author: Jason Ekstrand <<a href="mailto:jason.ekstrand@intel.com">jason.ekstrand@intel.com</a>>
AuthorDate: Wed Jun 6 10:24:01 2018 -0700
Commit: Jason Ekstrand <<a href="mailto:jason.ekstrand@intel.com">jason.ekstrand@intel.com</a>>
CommitDate: Thu Jun 7 11:23:34 2018 -0700
i965/screen: Return false for unsupported formats in query_modifiers
Cc: <a href="mailto:mesa-stable@lists.freedesktop.org">mesa-stable@lists.freedesktop.org</a>
Reviewed-by: Lionel Landwerlin <<a href="mailto:lionel.g.landwerlin@intel.com">lionel.g.landwerlin@intel.com</a>>
-------------------------------------------------
Based on the size of the regressions, and GeomPoint improving with the change
(only test which regresses with RBC), I'd say that above commit disables E2E
RBC for these tests.
Any idea why? Rendering looked fine before this change.
On GEN9+ GT2 machines, there's also 3-4% performance drop visible in GfxBench
onscreen ALU2 & Tessellation tests from this commit, and maybe 1% in GfxBench
Manhattan 3.0, but those regressions are slightly less than half of what the
E2E RBC improvement was.
Interestingly, this same commit also improved SynMark VSInstancing performance
noticeably on GEN7 & GEN8 (which don't support RBC).</pre>
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