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<base href="https://bugs.freedesktop.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - "Avoid waitboosting" now prevents all GPU boosting (e9af4ea2b9e7)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=107111">107111</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>"Avoid waitboosting" now prevents all GPU boosting (e9af4ea2b9e7)
</td>
</tr>
<tr>
<th>Product</th>
<td>DRI
</td>
</tr>
<tr>
<th>Version</th>
<td>DRI git
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Component</th>
<td>DRM/Intel
</td>
</tr>
<tr>
<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>freedesktop@nmacleod.com
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>CC</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=140459" name="attach_140459" title="Monitoring script and results">attachment 140459</a> <a href="attachment.cgi?id=140459&action=edit" title="Monitoring script and results">[details]</a></span>
Monitoring script and results
We've had reports of the Kodi GUI "stuttering" since LibreELEC switched from
kernel 4.14.49 to 4.17.3.
I ran a script that monitors /sys/kernel/debug/dri/0/i915_rps_boost_info and
noticed that with 4.17.3 the GPU never boosts out of the "low power" window.
It's the same when watching a video - the GPU is now almost always stuck in the
"low power" window.
git bisecting the kernel between 4.14.49 and 4.17.3 reveals
e9af4ea2b9e7e5d3caa6354be14de06b678ed0fa[1] ("drm/i915: Avoid waitboosting on
the active request") as the bad commit.
In the attached file you can see the script, and also the results of testing
many different LibreELEC/Kodi builds (corresponding to the builds here[2]).
With this script the first 30 seconds of a 4K video (Elysium trailer, on a
Skylake NUC6i5SYH outputting at 1080p) is played from local storage in Kodi. At
the end of the script a summary is output which includes the percentage of
"LOW" (ie. low power) and "!LOW" (ie. high + mixed) window samples. The script
is executed 5 times per build.
What is very clear is that from build 180616 (ie. #0616[3]) onwards - which is
when the LibreELEC kernel switched from 4.14.49 to 4.17.3 - the number of
"!LOW" samples is reduced to almost zero - ie. the GPU no longer boosts,
remaining locked at the "idle" frequency.
To rule out any changes in Kodi that might also be responsible I rebuilt build
180702 replacing only the 4.17.3 kernel with 4.14.49, creating build 180702a,
where now the GPU boosts as expected.
Reverting the bad commit from kernel 4.17.3[4] resulted in build 180702b, and
again the GPU is now boosting as expected.
Kernel 4.18-rc1 also has this non-boosting issue (same as 4.17.3).
With this commit reverted, the reports of "stutter" in Kodi with 4.17.3 (and
now also 4.17.4) are resolved[5, 6, 7].
Can this commit be reverted, or is there a better solution that doesn't hobble
the GPU?
Thanks
Neil
1.
<a href="https://github.com/torvalds/linux/commit/e9af4ea2b9e7e5d3caa6354be14de06b678ed0fa">https://github.com/torvalds/linux/commit/e9af4ea2b9e7e5d3caa6354be14de06b678ed0fa</a>
2. <a href="https://forum.kodi.tv/showthread.php?tid=298462">https://forum.kodi.tv/showthread.php?tid=298462</a>
3. <a href="http://forum.kodi.tv/showthread.php?tid=298462&pid=2744031#pid2744031">http://forum.kodi.tv/showthread.php?tid=298462&pid=2744031#pid2744031</a>
4.
<a href="https://github.com/LibreELEC/LibreELEC.tv/pull/2798/commits/914cadbafd09861f05244d4b985476414760823b">https://github.com/LibreELEC/LibreELEC.tv/pull/2798/commits/914cadbafd09861f05244d4b985476414760823b</a>
5. <a href="https://forum.kodi.tv/showthread.php?tid=298462&pid=2748603#pid2748603">https://forum.kodi.tv/showthread.php?tid=298462&pid=2748603#pid2748603</a>
6. <a href="https://forum.kodi.tv/showthread.php?tid=298462&pid=2748688#pid2748688">https://forum.kodi.tv/showthread.php?tid=298462&pid=2748688#pid2748688</a>
7. <a href="https://forum.kodi.tv/showthread.php?tid=298462&pid=2748696#pid2748696">https://forum.kodi.tv/showthread.php?tid=298462&pid=2748696#pid2748696</a></pre>
</div>
</p>
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