<html>
<head>
<base href="https://bugs.freedesktop.org/">
</head>
<body>
<p>
<div>
<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+"
href="https://bugs.freedesktop.org/show_bug.cgi?id=87726#c16">Comment # 16</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+"
href="https://bugs.freedesktop.org/show_bug.cgi?id=87726">bug 87726</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>You would need to measure current mesa with execlists=0 and ppgtt=1 to get the
current baseline.
Baseline: i915.enable_execlists=0 i915.enable_ppgtt=1
# Not sure if i915.enable_execlists=0 i915.enable_ppgtt=2 is functional enough
to # test
1: i915.enable_execlists=1 i915.enable_ppgtt=1
2: i915.enable_execlists=1 i915.enable_ppgtt=2
The biggest improvement in the kernel for this bug was from using an rbtree for
vma lookup, and improving the mechanisms for writing the GTT. (Almost)
Everything I had planned for this bug (since ~30 months ago) is almost in the
kernel, the last dregs can be found here:
<a href="https://cgit.freedesktop.org/~ickle/linux-2.6/log/?h=prescheduler">https://cgit.freedesktop.org/~ickle/linux-2.6/log/?h=prescheduler</a> (down to 37
patches!!!).
The remaining features are O(1) lookup for vma from a context (i.e. excellent
scaling of execbuf to very large number of contexts), context state caching.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>