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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [GEN9] 20% perf drop in windowed/composited GpuTest Triangle"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108598#c12">Comment # 12</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [GEN9] 20% perf drop in windowed/composited GpuTest Triangle"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108598">bug 108598</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>(In reply to Eero Tamminen from <a href="show_bug.cgi?id=108598#c11">comment #11</a>)
<span class="quote">> There was a windowed Triangle perf improvement in early December, along with
> large reduction in variance.
>
> Another clear perf improvement (and variance reduction) happened recently,
> between:
> 2019-01-22 14:34:34 af90b519a6: drm-tip: 2019y-01m-22d-14h-33m-29s UTC
> integration manifest
> 2019-01-23 16:59:31 198addb18e: drm-tip: 2019y-01m-23d-16h-58m-20s UTC
> integration manifest</span >
Only one thing of significance there,
commit 6e062b60b0b1bd82cac475e63cdb8c451647182b
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Date: Wed Jan 23 13:51:55 2019 +0000
drm/i915/execlists: Mark up priority boost on preemption
which should help prevent some surplus preemption loops and could definitely
have a small, variable impact on performance.
<span class="quote">> I think windowed GpuTest Triangle perf is still a bit below what it was
> originally (I need to check that from older data, I don't see it anymore in
> the trends).</span >
There's a tiny bit more work to come tweaking need_preempt() to avoid excess
preempt-to-idle cycles, but it should be diminishing returns.
Confidence is high that preemption was causing at least part of the problem
though.</pre>
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