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<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [Kabylake] RPS waitboost regression since v4.20"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109408#c7">Comment # 7</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [Kabylake] RPS waitboost regression since v4.20"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109408">bug 109408</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 Lakshmi from <a href="show_bug.cgi?id=109408#c6">comment #6</a>)
<span class="quote">> Reporter, can you verify the issue with latest drmtip?</span >
Yes, Lyude already has. And we've found so far that it isn't missing
waitboosts, as we've unconditionally applied the boost to all request waits and
still the performance is jittery on -tip. My suspicion lies towards something
else inducing latency causing the GPU to idle enough for rps downclocking to
take hold; that's likely to be vblanks (nothing else matters?). Optimistically
Lyude might be able to bisect, but it'll be slow, tedious and prone to
mistaking good/bad results. And there may well be more than one change leading
to this effect.
But for now the investigation mostly says it's not waitboosting per-se that's
changed between the versions.</pre>
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